GTA San Andreas - Invisible vehicles underwater

Somewhere near the bottom left corner of the map, there is a place with a pool of water and some trees(Back O' Beyond). One of the trees is leaning over, you can climb up it and jump in the water, but that's not what this post is about.

Drive a vehicle of some kind into the water, and then get out and look, you can't see the vehicle from the surface, only when you go underwater. This works with anything, even a hydra.