海底生物界是与水域基底相连的生活区域，可分为滨海海底生物界（光线可透射的，夏季温暖的水域底层）和深海海底生物界（暗的，冷的水域底层）。在海底生物界栖息的生物被称为海底生物。

• 浮游生物界
• 滨海生物界

The benthic zone is the ecological region at the lowest level of a body of water such as an ocean or a lake, including the sediment surface and some sub-surface layers. Organisms living in this zone are called benthos, e.g. the benthic invertebrate community, including crustaceans and polychaetes. The organisms generally live in close relationship with the substrate bottom and many are permanently attached to the bottom. The superficial layer of the soil lining the given body of water, the benthic boundary layer, is an integral part of the benthic zone, as it greatly influences the biological activity that takes place there. Examples of contact soil layers include sand bottoms, rocky outcrops, coral, and bay mud.