Underwater welding comes in two flavors, wet and dry.
Wet welding is impractical because of water
- conduction heat
-- do some electricity
Welding - pollution
- limit flux cleaning action/oxygen mask
Wet welding is poor, usually unreliable, and anything but low carbon steel can't work.
Drying (high pressure oxygen) welding is at least possible, and is fairly reliable. Use gas to dry weld area under pressure. It's much more difficult than ordinary welding. At present, sea welding is usually at the top (above sea level), welding after welding assembly. The repair of some structures is actually the only application of submarine welding, which is impractical for fixing the fixed parts or recovery structures of bolts.
