I reckon you want to listen to MidLandOne, weld the puppy if looking at a permanent
mooring type application. No way would I use stainless for anything underwater for more than a week or 2 in one go. I've seen it actually fizzing on the odd
mooring. Seen more fizzing on high tensile
gear though so just don't go there.
Also if doing a permanent mooring I'd not use galvanised chain or fittings, just use self-colour (sometimes called 'black'). Galvanising is designed to wear (word use issue) off and in doing so creates a tiny tiny
current. It is not unknown for this
current to like being there when the galv has gone and in doing so can make mooring
gear disappear faster. We never use galvanised products for permemently immersed situations like moorings.
Anchoring is a up and down thing so is different hence galv and SS can be used more.
Deeper you go the less oxygen and things can't rust without it. Mind you moorings rusting way are not common, wear is the one to watch for.
And a tip - if welding up shackles or anything for permenent underwater use, use the
cheap general purpose rods. The flasher the rods used the more likely they can cause greif.
Cable ties are OK but only for short term or
emergency use or on anchors where you can see them. Most have little UV stability and can wear off quickly in the wrong situation.
Another way of doing shackles it to do them up with a bloody big spanner and then peen the end of the pin over with a bloody big hammer. On a mooring I'd still prefer welding though.
Locktite is damn good as mentioned by some smart cookie above.
And the big thing - shackles are
cheap in the big scheme of things. Hence do everything you can to stop them coming undone and DON'T plan on re-using them, plan on having to cut them off. We see people putting
Rescue Steel and stuff on them so they can get them off easier later. Sadly most don't realise Mother Nature has a pile more balls than most people have so she can also get them undone just as easy and often does.