The Tavern

This is a pretty minor point but if the Wiki is correct, Ogres and Trolls receive no stealth penalty in shallow water. I would think that they splash water and make waves just like smaller races and should therefore receive the same penalty. It makes sense that they don't get attack penalty due to their size.

learndb has this to say:

which suggests tr/og get stealth penalties just like other races

I do not know which (if either) is correct.

I traced the logic of this - ogres and trolls do not get stealth penalties in water on account of their being a large-sized race. In fact, this partly uses the same check (player::extra_balanced()) that checks if you fumble attacks while standing in shallow water, so ogres and trolls can attack without penalty from shallow water.

Since this is size-based, it means Centaur and Naga also do not get stealth penalties.

Of these four, it doesn't matter in practice for Ce/Og/Tr, since those three have terrible stealth anyways. Probably 0 stealth since they typically favor wearing heavy armour. Na is the only one with good stealth, but thematically it makes sense for them, since they don't have legs and thus should be much less noisy in water. So while it's a bit odd to not penalize Ce/Og/Tr stealth in water, it may not be worth the effort to fix.