From Marine Protected Areas South Africa website:

After the 2011 National Biodiversity Assessment noted that offshore ecosystems were poorly protected, the Offshore MPA project (2007- 2011) initiated plans to increase protection of offshore ecosystems, which were advanced towards implementation during Operation Phakisa Oceans Economy. A total of 22 new MPAs were gazetted for comment in 2016 as part of a lengthy consultation process. The South African Cabinet granted permission to declare a revised network of 20 new MPAs in October 2018. It took several months to prepare the declaration notices and final regulations. This culminated in the gazetting of 20 new MPAs on 23 May 2019. These take effect on 1 August 2019 and expand the protection of South Africa’s mainland ocean territory to 5%.

From the Operation Phakisa website:

20 new MPAs, and two expanded MPAs were identified through Operation Phakisa‚ a presidential project to fast-track the development of South Africa’s Ocean Economy. The new MPAs will secure protection of marine habitats like reefs‚ mangroves and coastal wetlands which are required to help protect coastal communities from the results of storm surges‚ rising sea-levels and extreme weather. Offshore‚ these MPAs will protect vulnerable habitats and secure spawning grounds for various marine species‚ therefore helping to sustain fisheries and ensure long-term benefits important to food and job security.

From Government Gazette Staatskoerant:

The Southwest Indian Seamount Marine Protected Area in the Western Cape is an offshore Marine Protected Area in the 1200m to 5000m depth range lying approximately 93 nautical miles South of Stilbaai.

The purpose for declaring this Marine Protected Area is:

(a) To contribute to a national and global representative system of marine protected areas by providing protection to the benthic and pelagic ecosystems of the shelf edge, slope and abyss of this region;

(b) to conserve and protect rocky shelf edge, seamount and associated deep sea ecosystems;

(c) to conserve and protect the biodiversity and ecological processes associated with these ecosystems;

(d) to conserve and protect an area of life history importance for migratory species including seabirds, turtles, sharks and other fish; and

(e) to protect and provide an appropriate environment for research and monitoring particularly research on ecosystem description, resilience and change.