I crewed on a private sailboat for a summer after college and it was amazing: it's a paid adventure with great people in breathtaking places. Even the middle of the ocean is surprisingly beautiful. The most important pre-requisite is a strong stomach. It's likely you'll hit a storm where you will be levitating off your bed at the height of each wave for two days straight: seasickness is completely incapacitating and will make your captain regret taking you onboard. If you pass that and can clean and heat up a pizza, most captains will take you on all expenses paid, possibly with pay. There is a migration of boats from the Caribbean to New England in the spring and back down south in the fall. Try hitting the docks at the stopping over points in St. Barts, Martinique, Bermuda, or Newport.