From someone who lives 15 minutes from saltwater.....
NEVER NEVER NEVER run an RC ground vehicle in saltwater. Even if rinsed later, by the time you get it to a place to flush it, the damage will be done.
saltwater will destroy it quickly. I can't be any more clear on this.
I would love to run mine at the beach or even near in the dunes, but I will never even do that as the salt is in the air and can be in the sand far from the water.