The Joker Trumps an Ace - S1.E25

The Joker launches a new crime wave with robberies that appear to make no sense, such as stealing hairpins from rich women and a hole from a golf course. But the Joker knows exactly what he's doing. Batman and Robin are in pursuit and eventually invade the villain's headquarters. The heroes are placed in a chamber and are told if they can float for an hour, they'll go free. The Joker then begins to flood the chamber with poison gas. The Joker says the Dynamic Duo may not be able to swim in the gas "but you can drown in it!"