ú Newsgroup: news.answers ú Message-ID: <1992.May.1.scuba.faq@scifi.uucp> ú Subject: [rec.scuba] FAQ: Frequently Asked Questions about Scuba, Monthly Posting Archive-name: scuba-faq This posting was last modified on 1/6/92 to change the text involving scubasearches in a couple of small ways. I'm considering upping the frequency of the FAQ posting to twice a month. Too many sites do not respect the 30 day expiration that I put on the monthly posting. I'd appreciate comments. Please feel free to follow-up with comments or email them to uunet!bywater!scifi!njs or scifi!njs@uunet.uu.net. -=-=-=-=- Welcome to rec.scuba. The newsgroup is for discussion of scuba, diving, snorkeling, dive travel, and other underwater activities. Frequent topics are safety, equipment, and certification. We welcome postings from new folks and old hands. Rec.scuba has had a fairly flame-free history. Not that we don't speak out against practices that we disagree with, but we do try to avoid flaming people. Flaming for flaming sake is to be discouraged. Before posting to this group for the first time, please check the FAQ list (this posting), and also read the newsgroup news.announce.newusers, which contains many answers to questions about usenet in general. Summary of rec.scuba FAQ: 1. Differences between certification agencies. (PADI/NAUI/YMCA/SSI etc.) 2. New Diver buying first piece of equipment. 3. Some sources for mail order equipment. 4. rec.scuba archive sites and how to access them. 5. How to find out about dive destinations. 6. Basic discussion of thermal protection (wetsuit, drysuit, darlexx). 7. Liquid breathing in the movie "Abyss". 8. Scuba magazines and periodicals. 9. Diving in contact lenses. 10. What about Spare Air or Pony Bottles? Frequently Asked Questions: 1: I'm planning on getting certified. I've been to several shops, and they all offer different certifications. I've heard of PADI, NAUI, YMCA, NASDS and SSI. Which one should I go with? 1a: This question has frequently come up in rec.scuba. One of the discussion threads has been summarized as whosbest.txt in the rec.scuba archives at ames. See the explanation of Peter Yee's archive, below, for how to access the ames archives. The short, widely agreed answer, is that agencies all must follow a minimum standard set by an industry organization, so they differ less than you might expect. However, instructors differ a lot, and you should try to talk to the instructor you will be taking the course from and determine exactly what will be offered, and how you feel about them. Finally, some instructors add significantly to the standard course (and may also charge more). You should ask exactly what you are going to get for your course fees, what else you will have to buy, and where you have to buy it. 2: I'm new to diving, and I want to buy some equipment. Which piece of equipment should be the first? 2a: There are two schools of thought on this. One is that you should consider only purchasing your personal gear until you are sure what type of diving you like. This school believes you should buy only mask, fins, and snorkel, for fit and sanitary reasons. The other school of thought is that the rental gear you can rent, especially in tropical locations, is second rate and poorly maintained, and that gear you purchase will be better and more reliable. Typically, people agree that you should not buy a tank until you believe that you will be doing a significant amount of local diving. 3: Where are good sources for mail order equipment? All of the local shops seem to be very expensive. 3a: There are good reasons to pay retail for equipment from your local shop. Some shops allow exchanges if the equipment does not fit, even if the equipment has been used. Typically, the mail order places will replace equipment if defective or unused, but not if it just doesn't fit. You must decide for yourself whether it is worth the risk to order mail order. You should also consider the ethics of using your local shop to decide on brand and fit, and then mail-ordering. If you do decide to go with mail order, you might try the following sources: Performance Diver, Chapel Hill, NC. 1-800-727-2453. They carry a wide variety of accessories and dive gear, including wetsuits, backpacks, regulators, spearguns, lights, cameras, watches, and books. Overnight delivery via Federal Express for an extra fee. Their prices are not the best, but they have a lot of stuff. Diver's Supply, several locations, including Georgia, Alabama, and two shops in Florida. Have roughly everything. House brands and Beauchat. 1-800-999-DIVE. Berry Scuba, from Chicago. Also in Atlanta. 800-621-6019. Carry "packages", as do these other places, and seem to have most everything. American Water Sports, 6775 Wilson Blvd. Falls Church, Virginia, 22044-3370 ph: (703) 534-3636. These people seem to have the absolute best prices on Poseidon gear around. They will ship mailorder. Mail order regulator repair. Adventure Divers, Inc., (305) 523-8354. For orders, 800-PLAN-FUN, faxes at 305-763-1873. They prefer to use the fax only when people want quotes and can't get through to the 800 number, such as when they are ordering from another country. They sell, at a discount, Parkway, Beauchat, Oceanic, Zeagle, SSA, and Poseidon/Viking. They also fill orders overseas and carry metric gauges and computers. They do mail order regulator work. One year parts-and-labor guarantee. One year price guarantee, but American Water Sports had better prices on Poseidon. 4. Are there any archive sites for rec.scuba? If so, how do I access the rec.scuba archives? 4a: There are two rec.scuba archives. The first, and oldest, is maintained by Peter Yee. Peter has collected travelogues, equipment reviews, and so forth into pre-organized files. In Peter's own words: You can also use the SCUBA archives on ames.arc.nasa.gov. Send mail to archive-server@ames.arc.nasa.gov (or ames!archive-server) and use a subject with a line like "send scuba index". This will get you an index of articles in the archive. They are sorted by subject and you will that you get pretty much what you ask for. To get Florida info, try sending a subject of "send scuba florida.txt keys.txt". -Peter Yee yee@ames.arc.nasa.gov ames!yee Advantages to Peter's archives are that they are organized by subject, allow instant access if you have FTP, and are actually about the subject in question rather than just randomly containing that word or phrase. The second archive is maintained by (me) Nick Simicich. This is sort of a minimalist archive. There are over a years worth of articles in the backlog, and you can run an "egrep" against them and the responses will be organized and sent back to you. To use the archive, mail to uunet!bywater!scifi!scubasearch or bywater!scifi!scubasearch@uunet.uu.net. You place the search pattern you want in your Subject: line. The search is CaSe InDePeNdEnT. Up to 10,000 result lines will be sent to you if you put in a general enough search pattern. As an example, to find articles which contain the string "dive watch", "diving watch" or close approximations, send mail to scubasearch with "Subject: div.*watc". "div.*wat" would not be good because that would get you "dive...water". Another bad search pattern is "cuba" because that will select every article, because cuba is part of scuba. Try "\" instead. Multiple level searches: Supposing you want to find a posting that mentions accidents in the Cayman islands. You could search for "accident.*Cayman|cayman.*accident", and that would tend to find some of them, but it wouldn't find postings where caymans was mentioned in the subject line (for example) and "accident" was mentioned somewhere in the body. To get around this, I've added a syntax that the shell script will use to run multiple grep passes. You just separate the arguments to the successive grep passes with an &. For our example above, you could code "Subject: cayman & accident". The shell script will run grep against all of the files with the argument "cayman" as he search string, and then run grep again with the search string "accident" against the files that result from the first pass. You can stack these to an arbitrary depth. You can also get as complex as you want usng this feature. For example, you might want to do a search for articles that I didn't write with cayman in the subject. This pattern might do it: Subject: ^Subject:.*cayman & -v ^From:.*njs -v can be specified on a second or subsequent grep pattern (after the &, as shown above) and eliminates all articles that contain the grep target. This is not a hook for general grep tags. This is a special tag that changes the action of the shell script. You can limit your searching to a particular date range by specifying a line as follows: Searchdates: [fromdate] [;todate] The format of the date is pretty liberal, and can include patterns such as "01 Jan 91" as well as "1 year ago". You can leave out the todate, or leave out the fromdate just by starting with a semicolon. You can get further information about egrep patterns by sending mail to scubasearch with "Subject: help". There are more detailed instructions regarding the date and the inverse searching in the help file, as well. You can get a copy of this FAQ by sending mail to scubasearch with "Subject: FAQ". You can do a search for someone else by naming them in a reply-to line, either in your mail header or the message body. Advantages are that every posting is there. Disadvantages are that you will get random stuff which happens to mention your search string if it is not specific enough, and you might get tons of stuff you don't want. If you do make a successful scubasearch, consider editing the result and mailing it to Peter Yee for inclusion into the organized rec.scuba archives so that the next person has instant access to the information. I'm on a uucp path, so a scubasearch will take either several hours or overnight. 5: What can anyone tell me about diving in [Florida, Cozumel, Belize, Bonaire, Great Barrier Reef, etc.]? 5a: Seriously consider doing a scubasearch or looking in the archives at ames before asking your question. If there hasn't been any conversation on your destination recently, then by all means ask. 6: I'm thinking about buying a [wetsuit/drysuit/diveskin/Darlexx skin]. What are the differences between them, and what are they good for? 6a: Diveskins are typically made of Lycra or some other stretchy fabric. The warmth supplied is minimal. Typically, they are used to prevent stings from jellyfish, and to protect from accidental coral contact. Sport divers tend to wear skins in water warmer than 80F degrees, or under wetsuits, so that the wetsuit will slide on easier. Next up in warmth is the Darlexx suit. This is a suit that is similar to a diveskin, but which is made out of a fabric that slows water flow. There have been reported problems with the Darlexx fabric "delaminating" or coming apart. An alternative is made by Aeroskin, and uses polypropylene and lycra. Depending on how warm blooded you are, you might be able to wear Darlexx comfortably down to 72F. A Darlexx suit is a wetsuit. It does not fit like a diveskin, and is not really a substitute for a skin. Wet suits are made of neoprene rubber. The suits serve two purposes: They reduce water circulation over your skin, and the air impregnated neoprene insulates you from the cold water. At the worst, a poorly fitting wetsuit can ruin your dive by letting you get so cold that you get hypothermic, or by being so tight that it cuts off your circulation. If you are not well fitted by stock wet suits, you can have one custom made. Custom made wetsuits are not that much more expensive than stock ones, and fit much better. Wet suits come in several thicknesses and styles. People wear different styles of wet suits between 32F-85F. Most people find that temperatures below 45-50F are not comfortable for longer than a few minutes in a wetsuit. Dry suits are used by prople between 70F-28F. (For extended commercial operations at near freezing temperatures, heated water is pumped through a special suit or underwear set.) (Temperatures below 40 require special environmental protection for regulators, controlled use of inflators, and (hopefully) redundant breathing systems.) You should consider getting special training before you wear a drysuit. Even fitting the drysuit is not quite as straightforward as fitting a wetsuit. A drysuit is useful at a wide range of temperatures because you can vary the amount of warmth by wearing different underwear with the suit. 7: I just saw a really great movie called the Abyss. In it, they had a rat breathing liquid. Is that really possible? Is there equipment like that for humans? 7a: Yes, it is really possible. The rat was breathing liquid in the scene you saw in the movie. No, it is not done with people (except possibly with premature babies to replace missing surfactants). A widely cited study involved a single adult subject who had one lung filled with the liquid, but who had problems with pneumonia afterwards. It is considered highly risky. To pull an old thread on this from rec.scuba, send mail to scubasearch with the subject: ^subject:.*liquid scuba The liquid is a chloroflourocarbon, like freon, but with a higher boiling point. 8: I want to learn more about diving, and read a lot of diving magazines. My local newsstand only carries Skin Diver Magazine, which I hear a lot of derogatory comments about on the net. What other Magazines/periodicals are there, how do I subscribe, and what is the orientation of these magazines? 8a: There are many, many magazines and journals. I've created a file called scubamag, which I have placed in the archive at ames (see question 4). This file, too long to place here, reviews many of the magazines which are around. 9: Can I dive in contact lenses (contacts)? Is it safe? Will I go blind? 9a: The safety of contacts revolves around three issues: 1. Will nitrogen absorption affect the contacts? 1a. It is possible that non-gas-permeable contacts will get bubbles under them. For this reason, if you do wear contacts, they should be gas permeable or soft, or they should have holes drilled in them. 2. What is the likelihood of losing a contact under water? 2a. If you get water in your mask, and you open your eyes, you might lose a contact. It might stay in your mask, in which case you can possibly recover it. If you will be dangerous to yourself without contacts, (not able to see well enough to find the boat, and not used to dealing with things by sound) then this could be serious. You also have to consider the possibility that your mask will come off underwater, and that you will have to open your eyes to find it and replace it, and that your contacts might come off during this process. Losing contacts in the water has happened to a number of people. 3. What about the possibility of infection? 3a. You are always at increased risk of eye infection when you wear contacts. There is some possibility that there are bacteria in the water that will increase the risk of eye infection. Quick treatment in the case of contact related infection is important, and you are not likely to get that treatment on, for example, a liveaboard. At least one study has indicated that there is an increased possibility of Acanthamoeba infection when swimming with contact lenses. Other practitioners, who do prescribe soft contacts for swimmers, claim that there is no proof that the contacts were the proximate cause of the infections, but give no arguments as to why they feel that there is no correlation. 4. Are there any special considerations regarding soft contact lenses? 4a. Yes. Dr. Soni, Associate professor of Optometry at Indiana University has participated in a study which showed that 100% of soft contact lenses used in pool swimming were contaminated, when cultured. Normally, soft contact lenses are made up of a certain percentage of water. They absorb this water from your tears, and the amount of water they absorb is at least partially dependent on the salt content of your tears. When you swim with contact lenses, and you open your eyes, the lens readjust to the water content of the liquid you are swimming in. This causes them to stick to your corneas. It is claimed that it takes 1/2 hour after swimming for the lenses to equilibriate to tears, and that removal of the lenses before they equilibriate can damage the cornea, creating a "clear passage into the cornea for the bacteria from the contaminated lenses, which will cause infection." Even practitioners who strongly believe in swimming with contact lenses feel that disclaimers should be given when prescribing the lenses for this purpose. The lenses are not approved by the US FDA for swimming, but this may be just because no tests have been done. Some of the above information was extracted from an article from "Eyecare Business" magazine, the June '91 issue. Now, many people wear contacts in the ocean without problems, whereas others prefer prescription masks. If you have simple myopia, there are several brands of masks with snap in lenses that can be made up quickly in your dive shop. If you have a more complex prescription, there are optometrists who can glue lenses into your mask. Many people seem to really like these. Whatever you do, please avoid asking this question in rec.scuba. It is a very frequently asked question. Do a scubasearch on "contacts" or "prescription", and you will get many thousands of lines of opinion. People should follow up to this question by email if it is asked again [IMHO], unless they have new study information or something to quote that is substantive. (If it is substantive enough, I'll put it in as part of the FAQ answer.) 10: I'm thinking of getting a redundant breathing system, in case I have a hose failure or run out of air, and can't find my buddy. I've heard about something called "Spare Air", and also "Pony Bottles". Should I buy one? Or is there something better? 10a:First off, carrying a redundant breathing system is a good idea. There are a couple of important questions. (1) What are the types of redundant systems, and how much do they cost? (2) How much air do you need to be safe in case of a problem? (3) How likely are you to carry your redundant system with you when you dive and vacation? What sorts of redundant systems are there? First, by "redundant system" I'm referring to a system that will continue to work no matter how catastrophic the failure of your main system. Thus, I won't consider a Y valve a redundant system because of the fact that a burst disk could rupture or an O-ring could fail and exhaust your entire air supply, or, that because of an error or a bad gauge, you could exhaust your entire air supply. The three most frequently used redundant systems are (1) the bailout bottle, (2) the pony bottle and (3) the independent twin tank. Some British BCs have a small air bottle attached to the BC. With proper training and practice, it is possible to use this air for breathing. But since this isn't a straightforward regulator system, we won't discuss it here either. The bailout bottle is available in sizes as small as 1.2 cu ft, and as large as 3 cu ft. The best known brand is "Spare Air". The bottle has a regulator that must be switched on before use. Bailout bottles can cost between $200-$300. The ones sold at a discount by mail order houses are typically smaller bottles of older design. The pony bottle is a smaller spare tank that is actually a small standard scuba bottle, and attaches to a standard regulator. Many people use an inexpensive regulator on their pony bottles. You also need some sort of mounting system. Pony bottles can cost between $250-$350 depending on the regulator selected, the size of the pony, and the care you take while shopping. You can get a 13 cubic foot pony (in 2000 PSI and 3000 PSI models), a 17 cubic foot pony, a 30 cubic foot pony, a 40 cubic foot pony, and some other sizes. The independent twin tank is a second tank which is the same size as your first tank, and which has its own regulator. Since the two tanks fit into a single double tank bracket, they may look like a set of doubles, but, in fact, they are two separate tanks. The independent twin tank is a good option for certain specialty diving, like wreck penetrations or extreme deep diving, but I won't discuss it further here. Costs vary widely depending on how much the mounting costs, the type of tank, and so forth. How much air do you need to be safe? The following chart was produced by Dave Waller, and presents a picture that I feel is conservative. You should probably assume that, in an emergency, you will be breathing at one of the higher breathing rates. It also assumes a 60 fpm ascent rate, which is considered too fast by many computer models and some training agencies. Therefore, these numbers should be considered minimums, and any deviation from these conditions would be likely to cause these numbers to increase. # Total consumption (ft^3) # Total consumption (ft^3) without 15_ft Safety Stop [1] # with 15_ft Safety Stop [1,2] # Consumption rate (ft^3/min) # Consumption rate (ft^3/min) Depth | 0.5 | 1.0 | 1.5 | 2.0 # 0.5 | 1.0 | 1.5 | 2.0 -----+------+-------+-------+-------#-------+-------+-------+------ 80 | 2.33 | 4.66 | 6.99 | 9.32 # 3.42 | 6.84 | 10.27 | 13.69 100 | 3.10 | 6.21 | 9.31 | 12.41 # 4.19 | 8.39 | 12.58 | 16.78 130 | 4.45 | 8.90 | 13.36 | 17.81 # 5.54 | 11.08 | 16.63 | 22.17 150 | 5.48 | 10.95 | 16.43 | 21.91 # 6.57 | 13.13 | 19.70 | 26.27 200 | 8.48 | 16.96 | 25.45 | 33.93 # 9.57 | 19.14 | 28.72 | 38.29 Notes: [1] Total consumption includes 30 seconds at indicated depth, and a 60_ft/min ascent rate. [2] Assuming a 1/2 consumption rate during a 15_ft safety stop for 3 minutes. The numbers beyond sport diving depths are here only for reference, and not to encourage you to dive those depths. Redundant air only reduces one of the dangers you would face in diving to those depths. The largest Spare Air holds just under 3 cubic feet. The smallest available pony bottle holds 13 cubic feet. You can look at the chart, estimate your surface consumption rate, try to estimate what it would be in an emergency, and see where you fit in. It is almost certain that if you were diving deep, you'd want more air than the chart shows, as you might need to make a longer decompression stop. While some people have tested bailout bottle ascents from as deep as 100 fsw, it should be emphasized that these tests were not performed under stressful conditions. Typically, they are already neutrally buoyant, ready to ascend, and are consuming less air than they would in an emergency. Referring to the above chart, you can see that this would be possible for a diver who had a consumption rate of 1/2 cubic foot per minute, and who left immediately upon switching to their bailout bottle rather than taking time to get settled. People who prefer bailout bottles to pony bottles say that a pony bottle is too cumbersome to transport and wear and in fact is not carried, making it a useless boat decoration. Pony bottle proponents who carry their pony bottles with them when they travel say that they don't have a problem carrying them, and many wear them all of the time when they dive. They disagree that it is too hard/painful/time consuming to dive with a pony bottle. Opponents of bailout bottles believe that bailout bottles are useless diver decorations, mainly because the bailout bottles do not contain enough air for an emergency. They argue that from the time you switch to the bailout bottle, you have only enough air to ascend directly to the surface. You have no time to solve problems and little or no air to make yourself positively buoyant. A final argument is that a bailout bottle might actually give you a false sense of security, and make you less safe than you might be without one. Perhaps the final judgment should be made using the above chart, and the depth to which you plan to dive. If $$/cubic foot is a consideration for you, then you would probably prefer a pony bottle to a bailout bottle. Many people do all of their diving between 15-40 feet, and never dive deeper than 60 feet. These people would probably find the largest bailout bottle useful. If you go deeper, or if you might go deeper someday, consider a pony bottle of the appropriate size. -- Nick Simicich - uunet!bywater!scifi!njs - njs@watson.ibm.com SSI #AOWI 3958, HSA 318, NAUI #14065 Join the movement --- turn 'to bush' into a verb. Path: channel1!uupsi!psinntp!rpi!usc!cs.utexas.edu!uunet!europa.asd.contel.com!news.ans.net!yktnews!admin!bywater!scifi!scifi!njs From: njs@scifi.uucp (Nick Simicich) Newsgroups: rec.scuba,news.answers Subject: [rec.scuba] FAQ: Frequently Asked Questions about Scuba, Monthly Posting Message-ID: <1992.May.1.scuba.faq@scifi.uucp> Date: Wed, 1 Apr 1992 10:01:11 GMT Expires: 28 May 1992 Sender: njs@scifi.uucp (Nicholas J. Simicich) Followup-To: rec.scuba Organization: N.J. Simicich, Peekskill, NY Lines: 502 Approved: news-answers-request@MIT.Edu Supersedes: <1992.Apr.1.scuba.faq@scifi.uucp>