Sea Monkeys are underwater creatures that operate equipment (usually shaped to look like animals) by psychic power. They are gentle and peaceloving, but they have an offshoot called the Forsaken which tend to be not as nice
Sea Monkeys themselves are special figures, made by taking the head and torso of a LEGO® Life on Mars Martian and using a fin shaped piece for the tail instead of legs. All their ships and equipment are shaped to look like animals.
There is more information about Sea Monkeys here.