When Gordon and O'Hara break out the frozen paralysis the Joker put them in, they are further from the window they had been frozen at, and not quite in the same positions.
Venus is in the water with Batman, but after Batman rescues Robin from the clam her dress is completely dry.
One of the zoologists claims to see a goldfish in the fountain, which is being used to display tropical fish. However, goldfish are cold-water fish, and would not be housed with tropical fish, which are warm-water fish.
No responsible fish-keeper, much less a society of zoologists, would use an open and unheated public fountain to display rare tropical fish, which are extremely sensitive to water chemistry, temperature, and water quality.