Research lab-turned-hotel with typical accommodations in an atypical environment: 21 feet below the sea.. In Short The world's only underwater hotel offers guests the chance to explore the depths of the ocean while enjoying a romantic and peaceful getaway. Aquaphobes steer clear: In order to check-in to Jules, you must suit up, learn to scuba-dive (if you're not already certified) and dive 21 feet beneath the surface. Rooms feature hot showers, TVs, beds, kitchenettes. Windows offer a fish's-eye view of local marine life.