Bob, if you are a diver on the project you will need to take a commercial diving course. For working dives like you are describing it would be normal to have a deco interlock, a kind of bell or chamber for spending long hours decompressing. Also, it would be good practice to have a recompression chamber on board. For purposes of managing the project, one might be advised to hire a dive master from New Orleans or Houston. However, an experienced amateur diver who knows mixed gas and ancilliary equipment, tables and computers, etc, could do a quick inspection at 350 fsw. Even so, decompression could run into hours so be advised.