>>96471790
If you're after some bits I think you should look into the dredge.
It's a range meant for 40k, but once you remove backpacks, guns or the weird space marine boots I think you could end up getting some cool parts out of it.
lost kingdom miniatures has sea undead, but less of the fleshy kind, generally.

If you're looking for paint tips alone, I can't help, whenever the idea popped up I think people had some very different conclusions, with some thinking the best way is to make extremely pallid corpses with greenish folds, to others saying they should be very blackened or something.

The crew of the flying dutchman from pirates of the carribbean is a masterclass, but I think they avoided almost completely the normal traits of something realistically rotten and focused primarily on coral and marine textures, keeping the palette almost monotonous.