I think that most of his who laser weld stock stainless steel wire. Stainless lasers rather well.
As for soldering, I just pulled up this older Orchid thread:
I would suggest that the higher the karat gold solder you use, the less salt water and chlorine would be an issue. Gold solder would be my choice over silver for this application for that reason.
Trial run on scraps first?
Good luck.