Over in Japan, the Oita Marine Center features a funky fish tank that seemingly defies the laws of gravity, matter, and sensibility: thanks to some vacuum technology, the fishies can swim "out" of the tank so that you can feed them, pat them, etc.
Cool, yes, but this would be an absolute atrocity if anything went wrong. Those poor fish! Though I must say, some hilarity would certainly ensue if water started randomly spewing out all over a crowd of unsuspecting aquarium patrons. But still...those poor fish!