If you're serious about it, then go for it, man. I'm not sure I understand you, correctly, though. IT water training? I think you're combining two things. IT is an abbreviation for something with several names. Individual training, "Incentive" training, etc. Simply put, this is what the drill instructors do with you when you screw up. Keep in mind, it's nothing abusive, just a lot of calisthenics that will cause you to leave a puddle of sweat on the floor of the squadbay, or get sand caked on you when you're out in the "pit". You won't typically see this sort of thing after boot camp, though, unless you belong to a unit full of hard-asses.
The water training you go through is your swim qualification, which isn't too hard, depending on how far you wish to go. I can't really tell you what's required beyond WS-4(the minimum required to qualify), since I'm not exactly what you'd call a great swimmer. At the basic level, you'll have to swim for 25 meters (not hard at all), jump off a 10 ft high (I think) diving board in the proper position(arms crossed over your chest with both hands clasping your blouse and crossing your ankles after you jump.), and then you have to perform 3 different exercises. This first is treading water for 2 minutes (this is where I get tired, because I have little buoyancy.). After that, the next one (I forget what it's called.) involves leaning forward in a sort of "deadman's float" position(It's a position they teach you in case you're stranded in water to prevent you from drowning), under water for a minute(if I remember correctly.), but you can come up for quick breaths, as long as you do it correctly(there's a particular way you have to come up.). I've had some problems with this when I did it right after treading water, because I was out of breath. Once they let me catch my breath, I didn't have any problems with this. Finally, the last one for basic qualification is the fun one: the blouse inflation. At the start, you're in the water holding the side of the pool. Once they say "Go," you take a deep breath, go under water, grabbing both corners of your collar, blow all the air from your lungs into the collar of your blouse, and then clasp the collar of your blouse tightly to your body, so as not to let air escape. If you've done it correctly, your shoulders will be inflated, and you'll be floating. You have to stay like this for an allotted amount of time (a minute or two, I think.).
As far as the gas chamber goes, it's gonna suck your first time. It's CS gas, which to say the least, is not pleasant at all. It will cause all the snot in your nose to liquify and drip everywhere, your whole face will burn, and after you're done, if you take a leak, do NOT hold your dick to do it! The gas chamber, overall, is not THAT bad, though. It's only bad if you panic. The way it works is that they'll have everyone walk inside single-file, with their gas masks on, until all four walls have people lined-up facing the center of the room. Once everyone is ready, they'll tell you to close your eyes, take a deep breath, hold it, and then break the seal of your mask by sticking two fingers into the side. They'll have you holding this position for about 10 seconds. Then they'll tell you to reseal and clear your mask. Next, they'll ask you to close your eyes and hold your breath, and then pull the mask up onto the top of your head, and you'll hold it there for about 10 seconds (Don't open your eyes!). After this is done and you redon and clear your mask, they'll tell you to close your eyes, take a deep breath and hold it, and then completely remove your mask and hold it out in front of you (This is where people begin to spaz, or they make the mistake of breathing.). This will be done for about 10 seconds, unless someone spazzes and tries to make a run for the door. This is when the drill instructors and/or the NBC (Nuclear-Biological-Chemical) personnel spear-tackle the foolish individual, who is no doubt more miserable than ever. This can cause a delay here and there. Keep in mind, though, this is only in boot camp. Once you're at an actual duty station, you only have to do swim qualification and the gas chamber once a year, and it's nowhere near as "nazi-istic" as it is in boot camp. The last time I was in the gas chamber, we were wearing complete MOPP gear, and all they had us do was break the seal.
Like I said, man, if you're serious about it, go for it. In particular, I recommend the 2800 field for an MOS, but hey, I'm biased. If you've got any other questions, let me know.
