One of the weirdest dancefloors ever installed anywhere was made of Plexiglas and stretched across a 20,000-gallon tank filled with sharks at Qua in Austin, Texas. Unfortunately, it's now closed, but you can experience the next best thing at the California Academy of Sciences' weekly "Nightlife" events. Every Thursday evening the museum converts into a makeshift discotheque, using its various rooms to host DJs pulled from the city's best parties. Venture downstairs to Steinhart Aquarium, and, on select nights, you can dance next to a stunning variety of tropical fish. It might not be on the order of a shark-tank dancefloor, but we always thought that sounded kind of cruel anyway.