The "intertidal zone" is

Most trees would die if salt water covered their roots twice a day. Mangroves live exactly there. These trees and shrubs grow along coasts in the intertidal zone, the strip of shore that the tide covers and then uncovers, and there are about eighty different kinds of them.

Their home is a hard one. The soil is low in oxygen, and the water moves slowly enough for fine mud to settle. Mangroves also cannot survive freezing weather, so they grow only in warm regions near the equator.

Many mangrove forests are easy to recognise by their tangled prop roots, which make the trees look as if they are standing on stilts above the water. These roots let the trees cope with the daily rise and fall of the tide, which floods most mangroves at least twice a day.

The roots do more than hold up the tree. They slow down the moving water, so that mud settles and builds up the muddy floor. In this way mangrove forests hold the coastline together, reducing the damage done by waves, currents, tides and storms. And the maze of roots gives fish and other creatures a place to find food and to hide from the animals that hunt them.