The sea-bottom, or benthic habitat is composed of a variety of sediment types and is exposed to a wide range of water conditions, leading to the development of diverse plant and animal communities. Benthic habitats dealt with in this section are restricted to those that occur subtidally, from extreme low water to the continental shelf break at 200m depth. They are not exposed to air at low tide but are influenced by wave action and currents. The plants and animals in benthic communities are determined largely by the nature of the sea bottom, in combination with turbidity, depth, temperature, salinity and nutrient level. Offshore habitats range from bedrock, to coarse sand and gravel, to silt and clay.
Benthic plants depend on sunlight and occur only where enough light penetrates the water.
Benthic animals include a wide variety of invertebrates and fish.