I'm assuming the issue is with low tide since the ice sheets are static assets and don't actually float on the water, so at low tide the ice sheets are much higher beyond the jumping range.

I haven't tested much, but of the handful of times I've fallen in the water, or even intentionally attempted to swim to the ice sheets.
I was unable to jump from the water up to the ice sheet.

Some I assume was due to geometry of the ice sheet hanging more over my character preventing the jump as there was collision above my player.