There are a couple of dive companies in Lousiana that offer underwater welding to costumers, Oceaneering Int'l and Global Divers. I can't remember who you could talk to over at Oceaneering, but at Global you could try and talk to Tom Reynolds, 800-525-3483. I can answer some of your questions, I've been doing the underwater welding thing for 8 years. There are others out there, but I suspect like me they are offshore trying to do repairs from the hurricanes. Good luck.
Charles Welch