Okay, after the twin ice-diving dracs perforate the frozen lake surface, I find I can dive in and under. Is there anything of interest down there?

Yes, I have an enchanted waterbreathing item.

No, but there is under the water near Castle Volkair.

There are a couple of chests and a satchel...not much inside any of them but worth it if you're a 'find everything freak' like I am.

I never looked under there... feared getting lost even with my water breathing amulet I crafted.

Really? *goes off to take a look*