A forest with its feet in the sea.

A coastal mangrove forest lives between land and sea, where the tide repeatedly changes the rules. The mud can be low in oxygen and the water salty. Trees have to do more than remain upright. Different mangrove species solve these problems differently: some filter salt through their roots, while others release it through glands in their leaves. 'Mangrove' names a group of trees and shrubs adapted to this difficult setting, not one universal tree.

Some species develop above-ground roots that allow oxygen to reach roots in waterlogged soil. Others have long prop roots extending from their trunks. In Florida, red mangroves are familiar for these stilt-like structures, while black mangroves have upward-growing breathing roots. The forest's odd silhouette is not an ornamental flourish. It is visible evidence of what growing in a tidal place requires.

Root tangles slow water and help sediment settle, stabilising the shoreline. They also offer surfaces for attached organisms and sheltered spaces for young fish and other animals. A tree can be part of a nursery without having a nest in its branches. From a boat, the water's edge might look like a simple line of green. Move your attention downward and the line becomes a three-dimensional habitat, connecting muddy ground, moving water and the canopy above. A boundary on a map can be a whole neighbourhood on the ground. That is one reason a coastline is worth reading slowly.