Agree with gcarter and emorelra on the above.
1) I understand how it is bad to hold your breath if you are ascending, but why is it bad to hold it underwater? (if you are not ascending)
The only thing that I can think of adding is to not confuse breathing "at the top" of your lungs or "at the bottom of your lungs" with "holding your breath." Like gcarter said, don't close your throat, and you'll be fine. But for buoyancy purposes, it makes sense to breathe "at the top" or "at the bottom" so long as you're not holding it.
2) Is purchasing a tank worth the trouble? cost effective?
Generally, if you have to ask, no. It does save you a return trip, though, to drop them off. This can be a big issue if the closest dive shop to you is an hour away. What the posters above said!
3) I am planning on buying a GoPro, if I buy the flatlens and install it. Will that negatively affect the picture quality out of the water? I am asking because I am planning on using the gopro for skydiving too.
Ah, here's something I can add...
There's one sitting on my desk right now that I've been using, even though it's not mine.
My buddy will probably read this and want it back.
It seems that GoPro owners are talking a lot about the flat lens - especially the divers. I haven't visited the GoPro forums to see what sort of advantage they think a flat lens will bring them, but it seems counterproductive to me to seek a flat lens for underwater use, based on my experience with several of my own cameras, and now my buddy's GoPro.
Underwater, as light passes through the water, through a flat lens, and through the air before hitting your eyes or a camera's sensor/film, there is a magnification of about 25% and a "zoom" of about 30%. That is, when you shoot with a flat lens camera, everything looks bigger and closer than it does topside... Just like it does when you're wearing a mask. A domed port helps to offset this, as it "zooms out" and demagnifies and gives a "wide angle" view. This wide angle is one of the things that makes the GoPro such a terrific little camera... Especially when underwater (to help counter the natural zoom) and whenever doing extreme sports like skiing and snowboarding and mountain biking and skydiving. The wide angle simply lets you see more... And motion seems more distinct than it does with a flat lens.
My buddy is calling the wide angle view a "blur," which isn't what it really is... But I assume that he's gotten that from the GoPro forums or something, where there is apparently a general concensus that a flat lens - which would "un-wide angle" the camera like a common digital camera - would be a benefit.
This is not the case if you're shooting underwater - or whereever you want to minimize the effects of shaking and broaden the viewing angle, like with extreme sports. With a flat lens, the camera would also be a lot more sensitive of where it's pointed, since the angle is less wide.
No... For skydiving and underwater use, keep the domed port. Normally, camera guys pay big bucks to add them to their systems. The fact that the GoPro already comes with one installed is the whole point of the GoPro.
If you are going to use a flat lens, you might as well just shoot video using your cell phone... At least for skydiving anyway. Try it - that'll give you a good feel for why you'll want to keep the domed port.
5) is it bad to workout after diving? i.e. go to the gym for a couple of hours and run a couple of miles or swim?
No.
If it was, then we'd all be in a lot of trouble swimming back to the boat or dock or whatever. Respiration and circulation are what rids body tissues of residual nitrogen, and increasing them only serves to increase the speed at which residual nitrogen is dissolved and expelled. The concept of "no exercise after diving" is a wive's tale. if it wasn't, Navy Divers, SEALS and submerged assault forces would be in a lot of trouble for running and shooting and generally "exercising" after long dives.
6) how many dives until a new diver should give advanced open water a shot?
Go for it when you feel confident to learn more. Most experienced divers consider "Open Water" and "Advanced" as complimentary, and sort of "part 1" and "part 2" of the same course anyway, and there is no minimum number of dives that the agencies require, so... Do it as soon as you feel ready.
