Provide your best answer for the following question. Give ONLY the answer, no other words or explanation.
For example:

Answer: <most likely answer, as short as possible; not a complete sentence, just the answer!>.

The question is: an animal that moves quickly through the water is a
swordfish
Dolphin, Cheetah (wrong answer, but could be a fast swimmer in a pool), Porpoise, Shark.