It's beginning to look just like an...

[Sacred Jellybean]

I would think that underwater levels and swimming controls are notoriously more clunky and frustrating. In the 3D Mario games, they never did seem to nail down a more intuitive method of both swimming in all directions and jumping out of the water. I remember yelling at Mario, as though it were some extra-controller maneuver, saying "no, up, UP ya dumb bastard! Arrgghh!"

I was always partial to the breathtaking (at the time) snow and ice levels in Donkey Kong Country.