:help: sigh...jokes just aren't funny if you have to explain them. Anyway, the Oxygen Bar is just that...a bar where people go to breath oxygen as a pick-me-up. The joke is similar to any joke that has someone or something walking into a bar....as in "A man walks into a bar.....yada, yada"...only this time it's a fish...but instead of walking, he's swimming...ofcourse.

The bartender asks him what he would like...but being just a fish, all he is going to do is sit and stare....fish don't talk..lol. The bartender is so tired and overworked he gets the fish(which is really in the bar's aquarium) mixed up with an actual bar patron. That is the premise of the joke. You just have to imagine all of this as it happens.