Who ever heard of asking a cruise-ship captain to detour to a prime snorkeling site?On SeaDream Yacht Club's 344-foot twin ships—which sail the Caribbean and the Mediterranean—you may wind up in a vacant cove marveling at stingrays. Beyond flexible scheduling, the two 55-stateroom yachts carry dozens of water toys, a 24-hour self-service pantry for late-night treats, an Asian-themed spa, slot machines, and all the personal attention a staff of 89 can deliver. Despite such sophisticated service, these ships are far from formal: no tuxes, no gowns, and there's open seating even at the captain's table. Seven-day sailings start at $315 per day, midnight snacks included. 800/707-4911;