Which of these aquatic animals is NOT a mammal?

Which of these aquatic animals is NOT a mammal? Welk van deze waterdieren is GEEN zoogdier?

en Which of these aquatic animals is NOT a mammal?

Shark
Whale
Dolphin
Porpoise

In conclusion, the aquatic animal that is not a mammal among the options provided is the shark. While the dolphin, sea lion, and walrus are all mammals, sharks are a type of fish belonging to the class Chondrichthyes. Therefore, the shark is the correct answer for the aquatic animal that is not a mammal.