Susan Johnston., Age 13, of Margate City, N.J., for her question:

What is a manatee?

There is an old rumor that the manatee has been mistaken for a mermaid. We know, of course, that the mermaid is a mythical creature who never lived on land or sea. But we are sure of one thing about her   she is a charming beauty. If the bulky manatee were really a mermaid, oh my, we would have to change our notions about our glamorous, imaginary mermaid.

The manatee is often called the sea cow, and in many ways she is like a Water¬dwe7ling counterpart of the cow who enjoys life on the land. Both are big and bully animals, gentle at heart and rather lazy in their ways. Both of them have deep, mooing voices. Both cows and sea cows spend hours every day munching their plant food. Both bear big, live babies and feed them on mother's milk, and both land and sea cows are affectionate mothers.

But here the likeness ends. The manatee has n0 back legs at all, and her front limbs are a pair of paddle shaped flippers. Her big body is somewhat like that of a porpoise, perhaps eight feet long and weighing almost a quarter of a ton. Her bulky body tapers to a wide, flat tail which is rounded at the tip and Very useful for swimming.

The manatee has a huge head and a monstrous mouth. Her upper lip is split down the Center, and she uses the two halves for grabbing water weeds. A sharp eared. Listener can hear her munching her salads from a distance of 200 yards. Her leathery skin is grayish black, dotted with short and stubby hairs. Around her mouth she has a beard of longer bristles.

The sea cow is not an ocean going animal. She enjoys life in shallow coastal waters and marshy swamps where there are enough water weeds to provide her with 60 to 100 pounds of food a day. She may live in salt water or fresh river water. Most of her time is spent floating and munching in the weedy water, where her big body is almost invisible.

Manatees like calm, warmish water far from rushing rivers and tossing tides. Some live around the west Indies and others off the shores and down the lazy rivers of Africa. Many sea cows enjoy life off the shores of sunny Florida. Some live off South America where they are often hunted for their leathery hides, their oily blubber and their rich, red meat.

In April or May, Mrs. Manatee gives birth to a chubby pup, weighing perhaps 40 pounds. The baby is taken at once to the surface for his first breath of air. Later. He is taken up to breathe every four minutes, day and night. Mr. Manatee is a devoted father, and when mama, wishes to rest, he is pleased to take over the duties of babysitting.