Diving the south coast of South Africa/Twelve Mile Bank

The dive site Twelve Mile Bank is an extensive offshore rocky reef, south of Cape Agulhas, near Struisbaai in the Western Cape province of South Africa.

Understand
This is the second to southernmost recreational dive site on the coast of Africa, and has a reputation among spearfisherman for plentiful fish.

Position

 * S35°01.300' E19°55.473'

Name
The name "12 Mile Bank" is a simple description of the distance offshore of the reef.

Depth
Maximum depth is about 36 m. and the top of the ridges are about 30 m. (Average depth of a dive is likely to be about 32m.) Minimum charted depth is given as 26 m.

Visibility
Visibility can be quite good, in the order of 10 to 15 m, but not much data is available.

Topography
The bank is a reef of apparently hard sedimentary rock, much of it fairly low profile, with higher profile roughly parallel ridges and gullies, with relatively steep slopes. There are occasional sandy patches in locally low areas.

Conditions
The site is exposed to the weather, wind waves, and swell from all directions, so should be dived when the weather and sea state forecast is good.

Get in
This is a boat dive. The site is about 12 nautical miles (22 km) south of Cape Agulhas, and 36 km  by boat from Struisbaai Harbour, where there is a large public access slipway in good structural condition.

Marine life
The flatter areas are dominated by a spiny kelp forest of variable density, with more colourful sessile invertebrates such as sponges, octocorals and bryozoans on the steeper surfaces. A variety of fish typical of south coast reefs swim above the rocks.

Hazards
Getting lost while surfacing, particularly if decompression is fairly long. The site is far out to sea and the strength of the current is variable. Be cautious with decompression, it is a long way to the nearest chamber.

Skills
Certification for the depth, which will generally exceed 30 m, and the ability to deploy a decompression buoy are strongly recommended.

Equipment
Delayed surface marker buoy and reel or spool. Nitrox will make the dive more cost-effective by allowing a significantly longer dive time for a reasonable amount of decompression, taking into account that the nearest chambers are at Cape Town and Mossel Bay. Make sure there is oxygen on the boat.

Nearby

 * - popular spearfishing area
 * - popular spearfishing area

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