November 2006

By Michael Ange

Q: I'm shopping for a new BC. I know that fit is important, but how do I tell in the shop if a BC fits properly?

A: You're right that fit is important. In fact, it's the most important thing to look for in a BC. While it can be difficult to get a true feel for a BC standing on dry land, here are some steps you can take to get a better idea of how well it fits. When you find a BC you like, mount it to a tank first, and then try it on. This will give you a feel for how it will wear when exiting the water, returning to the boat or making long surface entries. Tighten up the cummerbund and all the adjustment straps to achieve a nice snug fit without restricting your movement or breathing. Walk around a bit and turn at the waist. The tank and BC should move with you, like an extension of your body. Now look in a mirror. Ideally, all the straps should be on the slightly smaller side of the middle of their adjustment range. This allows you to open up the BC when you're wearing a thick wetsuit or dry suit or to tighten it when you're wearing only a swimsuit or dive skin. Inflate the BC all the way. If there is body squeeze, make sure it won't restrict your movement or breathing. Follow these steps, and you should achieve a proper fit that will transfer easily to the water.

One more piece of advice: If the BC is weight-integrated (and most new models are these days), make sure you can find and pull the weight releases without looking, without thinking and without too much effort. Load the weight pouches with your usual amount of lead and practice the ditching technique in the store to make sure you can quickly dump your weights in an emergency.

|| |---| | | | Photo by Stephen Frink|

Q: In my open-water class, the instructor repeatedly stressed that we were never to go into the dreaded "overhead environments." Then, on my first dive as a certified diver, this same instructor starts leading people inside part of a ship sunk as an artificial reef. I recognize that the wheelhouse of a "diver safe" wreck probably isn't as dangerous as a true underwater cave, so what are the practical rules or guidelines for dealing with this kind of situation?

A: Unfortunately, some instructors tend to practice the "do as I say, not as I do" rule. Of course, the whole system breaks down when they take new divers along when they "do." Your instructor's actions probably indicate that even though you are a novice, he had great confidence in your skills and it's probable that the area of the wreck you swam through was stable and had been cleaned of entanglement hazards. However, the instructor was still wrong. The practical rule is simple: You should never swim into an overhead environment until you have been properly trained to evaluate the risks and have obtained the skills necessary to meet the challenges posed by those risks. Most training agencies offer a one- or two-day recreational wreck diver course that help you develop these skills.

Q: I love diving but it leaves me cold--literally. I'm never truly warm enough. How can I ensure the shivers down my spine are ones of excitement, not hypothermia?

A: If you are chronically cold underwater, it's time to re-evaluate your exposure protection. For starters, how old is your wetsuit? The insulation in a wetsuit comes from tiny gas bubbles trapped in the neoprene foam. Over time and repeated use, these air bubbles get crushed and lose their insulating ability. If your suit is more than five years old, it's probably time to shop for a new one. A new suit can leave you cold, too, if it doesn't fit right. Look for a suit that has a wide range of sizes and keep trying them on until you find one with no gaps under the arms, in the crotch or behind the knees. Underwater, these gaps can work like pumps, flushing water across your skin and costing you precious warmth. When you find a suit that fits, you may be surprised at how tight it feels. You need to have a full range of movement and must be able to breathe comfortably, but a wetsuit that keeps you warm at depth is probably not going to feel super comfortable when you wear it at the surface. It may also be time to step up to a thicker suit. If everyone else uses a 5mm, maybe you should go for the 7mm. Or think about layering. Adding a hood, hooded vest, heavier gloves and booties may do the trick if your core wetsuit is in good shape and fits properly. How deep are you diving? All wetsuits compress at depth, losing some of their insulating ability while also allowing more water to enter at the wrists, ankles and neck. For this reason, I also recommend to my clients that they avoid high-stretch wetsuits, particularly if they routinely dive to depths greater than 40 feet. Suits made of high-stretch neoprenes tend to compress more than traditional wetsuits. Finally, have you considered a dry suit? By keeping water off the skin and allowing divers to adjust their thermal protection by layering insulating undergarments, dry suits are simply the best way to stay warm underwater.

Q: I tend to travel by myself, which means I always get paired up with some random buddy on the dive boat. Some have been great, but most have been duds. Is there such a thing as safe solo diving? And how do I get the boat crew to let me do my own thing?

A: Solo diving has been a controversial topic in the industry for several years now. At least one agency (TDI/SDI) offers a certification for solo divers, but many dive operators in resort destinations still do not allow solo diving, even if you have the proper training and equipment. Those that do allow solo diving generally require you to sign a special release form, which you must provide.

The better option is to make the buddy system work for you. Take a few moments before the boat leaves the dock to speak with the divemaster and ask him specifically if you can be paired with a diver who has experience equivalent to your own. There is a natural tendency among boat operators to pair people they perceive to be weaker divers with divers who they perceive to be stronger; the theory being that the more experienced diver will help his buddy out if minor situations occur. By requesting a more experienced buddy or a buddy with a higher level of certification, you can short-circuit that process. Also, remember that diving is a social activity, so be social. Talk with your boat mates, find out what their interests are and their experience levels. Spend a little time at the resort getting to know your fellow guests and you may have the opportunity to step on the boat with a pre-selected buddy who you enjoy diving with.

Q: Maybe I missed it in my open-water class, but why is the maximum recreational depth limit set at 130 feet?

A: There are numerous theories on how the depth limit came to be, ranging from the impairment of nitrogen narcosis to the performance limits of early scuba regulators, but as a matter of practicality, 130 feet works out pretty well for recreational diving. Depending on which set of tables (or which computer algorithm) you use, you only get about five to seven minutes of no-decompression time at 130 feet. That's not a lot of play time, and going deeper only cuts into it even more. Then there's tank capacity to consider. At 130 feet you are experiencing nearly five atmospheres of pressure, which means every breath you take requires nearly five times as much air from your cylinder. You can exhaust a standard aluminum 80 pretty quickly at that depth. Nitrogen narcosis also becomes a significant factor for most divers at 130 feet. The experts say that 100 percent of divers actually start to feel some narcosis at 100 feet, and it only gets more pronounced the deeper you go.

Got a question you need answered?
E-mail it to edit@scubadiving.com, or write to Ask An Instructor, 6600 Abercorn St., Suite 208, Savannah, GA 31405.