There is nothing more frustrating to a consumer than being asked for an imprint of a credit card at the beginning of the trip and discovering numerous add-ons once the relationship ends. Inquire before hand what items or services are considered extra and what they cost so that there is no misunderstanding with the dive shop or vessel owner. Make sure that the understanding as to extra expenses is documented in any charter agreement. Know ahead of time if there are charges for such items as fuel, snacks, beverages, sun screen, ice, tips, taxes and insurance costs.