As Mother always said, “The best cure for any lackluster vacation is a themed voyage on the high seas.” All right, she never said that, but the advice is still sound. While any run-of-the-mill cruise offers a host of fun incentives (think epic buffets and luxurious staterooms), a themed cruise has the added benefit of a built-in conversation starter. Whether you’re a cigar enthusiast or a history nut, we’ve put together a list of the best themed cruises to help you plan your next ocean adventure.