On the level on which you have to save the creche of turtles, go to the chef.
Charge into the water without the chef game starting. When in the water, swim
to the surface and edge. The game will 'pull' you back to the chef (as if you
had lost the chef game). You should now be 'swimming' in the air!!
You can fly-swim anywhere on the level, but if you touch thewater, you will 
lose the swim-fly cheat. This effect ends when you leave the level.