A platform affected by water. It is a platform affected by gravity, thus if placed outside of water, the platform will drop onto the ground. If it lands on water it will always float to the top of the water. If there is a ceiling in the water it will pretty much stick to it since it tries to get to the top.

Additionally, floating platforms could get slightly pushed into the water when Tux or badguys land on them, sinking a bit further if buttjumped or hit by something big, like a Crusher. As a default sprite I would suggest the ice floes.