From now on I should just go straight to edisoncarter's site. He's got a cheat for the GameShark that raises the water lever throughout the streets of San Andreas.
And of course, there's a movie. (The link should work here, it needed to be edited on ed's site.)
Read further down on his site for info on spawning boats, a must for the newly created canals on the GTA landscape.
He's also remarked about a potential cheat for Mother Nature taking back the streets to give the appearance of an overgrown post-nuclear world. This would work well coupled with the cheat that eliminates the car traffic and causes all pedestrians to attack you. Kind of a 28 Days Later motif. It would be even better if there was a cheat just to spawn those zombie looking guys in Palomino Creek.
Someone should start talking to the guys who made the GTA Leatherface movie about this.