Confirm to permanently remove your answer!
You should NOT use austenitic stainless steel (304, 316, etc.) in stagnant sea water because of stress corrosion cracking concerns.
There are many incidents that fasteners designed to be submerged in sea water had to be replaced with either super duplex or galvanized carbon steel.
When designing, include a section in the Fastener Specification for material used in submerged application. Verify the material during design reviews, document with a checklist.