Eh, the water's not icy cold. So it's not great, sure, but it could be worse. When they get out though, Link might grab some Spicy Elixirs to help warm them up.

Right now though, he pushes on the log. The water carries them along, as the light becomes brighter, and brighter.

Until finally, the cavernous space opens up to the sky - and before them is a massive lake, filling in the valley where three mountains converge.