I was talking about this on IRC, and I want it to be officially recorded that this idea exists.
As we all know, the Swim charability is broken beyond imagination. It's just a cheap modification of Fly. Here's what Swim SHOULD do:
1. The moment the character leaves the water, they should switch to their jump state.
2. While in water, their personal gravity is reversed and weakened, so that they gently float up to the surface (perhaps a variable in the character's skin could be used to set their density). It would have to be tinkered with so that the character doesn't actually leave the water, but just pokes his/her head above it.
3. Pressing Jump should make the player move up towards the surface, and pressing Spin should make the player move down towards the bottom. When Spin is pressed, they would also temporarily enter their attack state for a fraction of a second, so they can kill enemies.
This would actually give people a REASON to set Swim as an ability, because it would be useful and wildly distinct from any other move. What's more, the altered controls would allow level designers to play around with interesting new challenges in underwater levels, intended for Swimming characters.
If you guys do not put this in a future version, I will be very disappointed.