Well, his torso should rotate up and down a bit... (in Blender he does). The different speed is now scripted not very well, I just changed the hangle physicals of the clonk. Perhaps you know a better solution for that or we could implement something in the engine. But the method you mentioned, adding an offset isn't very good in my opinion (changing actions, would result the clonk to make a jump and the clonk wouldn't be at the position he is shown).

Yes, a DiveIdle animation would be a good idea, but I had no idea, how you actually move, when you want to stay at a position underwater.