A cruise is surrounded by water, and there’s no better way to take advantage of that than to book a cruise that lets you swim — or sail or snorkel — off the back of the ship from a retractable marina. Luck into a warm, sunny day in a gorgeous harbor in, say, the West Indies or the Eastern Mediterranean, and banana boating through the surf may just turn out to be your most treasured experience. Here, seven ships with great water sports programs that offer everything from diving to snorkeling and kayaking ... and even surfing and submarine rides.