The ESC maybe waterproof... and the receiver maybe be sealed and waterproof... but the motor is not.. it probably can handle a small puddle or two... but then there are the batteries (probably the most expensive of them all) they are not waterproof... and don't forget about the bearings.. they will rust as well... so waterproof isn't so waterproof after all..

The Slash can take a moist dirt track or even a puddle or two.. but take care and understand that these are electric cars with some metal mechanical parts... water is not a good thing..

Also remember that if running in snow, that if you are running near or around streets, sidewalks and driveways, that the salt will cause metal to corrode faster...

Dirt good... grass ok... mud bad.. water worst..

Jerome