I have been renting from Bret for years. And, as a result, I know the rules--never ride in salt water. I rented two bikes for a week and never even rode near the bloody salt water. Then he charged me an extra 15 dollars for destroying the chain (it was rusty he claimed); not to mention it was already rusty when I first got the bike. But he wasn't able to provide photos for this claim. My advice would be to make sure the chain isn't rusty and everything is in working condition before you hop on the bike. If not, you better call him and demand a new one. Otherwise, he'll claim that you have destroyed his bike. Bitter.
Cons: Hidden charges