The deposit exists because a board is worth more than a week of hire and because things get left on beaches. It is not a profit line and it comes straight back when the gear does.
We will take cash, a bank transfer, or a copy of your passport with a signed note, and honestly we prefer the copy. Ten years of doing it that way has cost us two masks and one pump.
No deposit on a snorkel set at all. They are cheap and arguing about them would cost more than replacing them.