well, from what i have herd the life exspectancy ranges from 2 to 10 years, it tears your body up pretty bad from the all the compression chambers and time spent in them.
now the way it was demonstrated to me was the number one rule for underwater welding is Never turn your back on your ground. by that i mean you have your stinger in your hands infont of your body and your ground must be faceing you in the same matter in front of you. the reason for this is because water conducts current (obviously) so there for the current is constantly flowing between the two, hence if you turn your back then the current will flow from the ground through your body to your stinger(DCEP). not good. now because of this hazzerd there is someone above water with a big blade switch turning the weld current on only when the welder is ready to strike up an arc. as far as electrodes used i'm sure there is somthing unique about the ones they use but from what i could see they looked just like a lincoln excalibur 7018. the only difference was they have to run a 1/8" rod at about 450 amps because the the water surrounding the arc cools the puddle so rapidly.
so what ever you choose becarful please, it is very dangerouse. i won't lie i would like to try it atleast once. hopefully i'll get back to the ship yard where i seen it and get a chance on it. though if your going to be a CWI i think you will make great money if not just as much or more, or atleast you will be able to work longer and not have a tore up body you know what i mean?
Jeremy