Health and safety for under water welding?

Answer 1

I seem to recall that this is one of the most dangerous jobs on the planet. All sorts of health and safety issues from the decompression to the diving equipment(mask,suit, breathing apparatus) and also making sure that the welding equipment does not damage your diving equipment.

I'm guessing but I'd say those were the primary concerns

Answer 2

You need air both for you and for welding. Forced air blows water away. Operator error,water currents,marine life.