Chill Ya To The Bone

You muster your strength and swim into the lake. You push against the current that threatens to pull you under at any moment. As you reach the center, you can see something in the middle of the whirlpool where the water opens up into a small circle. Is that... a room? Too late to ponder now, you're drawn in, falling into the area below. On the way down you find 85 gems.

Under the whirlpool, a waterfall floats you into an underground lake. As you pull yourself from the frigid pool, an icy palace opens before your eyes. Thick layers of ice coat the cave's interior and ornate carvings decorate the walls. Your guide stands on the shore, shaking out her fur. She inspects the surroundings, and you do the same. You realize there is no discernible exit, though some of the ice looks thin and even cracked in some spots along the walls.

What do you do?