The life of manatees

Also called sea cows, manatees might not immediately resemble your average land-based bovine, but they do share a number of their characteristics. They are bulky, generally peaceful creatures and spend a large proportion of their time grazing on plants; in fact, they’re the only marine mammal with an exclusively vegetarian diet.
Surprisingly graceful in the water, they use their powerful flippers and tails to navigate tropical coastal regions and river networks. Their average speed is just eight kilometres (five miles) per hour, but they are able to reach 24 kilometres (15 miles) per hour for short spurts.
Although they never venture onto land (like whales and dolphins they’re even born in the water) they’re actually more closely related to elephants than other water-based animals. They also need a ready supply of air; the longest they can go submerged is about 15 minutes.
Due to their slow movement and typical habitat coinciding with highly populated areas, manatees were extensively hunted in previous centuries. They remain vulnerable to extinction to this day because their tendency to swim near the surface means they often fall victim to motorboat propellers and fishing nets.