The waters of Cape Town include the Atlantic seaboard, which is cool to cold temperate, and False Bay, which is also cool temperate, but significantly influenced by the warmer waters brought down the east coast by the Mozambique current and the Agulhas current, and has some similarity to the South Coast.

Cape Point is accepted as the boundary between the cool temperate South-western Cape bioregion of the west coast, and the warm temperate Agulhas bioregion of the south coast. Unlike the other boundaries between the marine bioregions, which are diffuse, the ecosystems vary quite distinctively over a short distance at Cape Point, due to the change from the dominating influence of the warmer Agulhas current to the east to the cold Benguela current to the west

There are many endemic species of fish, invertebrates and seaweeds, as well as a variety of other more wide ranging organisms, and a large number of shipwrecks, some of which are highly regarded as dive sites. False Bay is occasionally host to wandering fish from warmer regions, and occasionally even turtles, brought in on the currents from the east coast.

The mountainous Cape Peninsula, which separates the Atlantic Ocean from False Bay, also protects the coastal waters on each side from wind and waves from the other side, making it possible to have year round diving, but seasonal variations in where to dive and what to see, as there is a significant and noticeable difference between the ecosystems on the alternative shorelines.

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