Old name for Algoa Bay was Angra da Roca named in 1488, by Bartolomeu Dias when he was the first European to land there. He planted a wooden cross on a small Island now, St Croix or Santa Cruz island. he named the bay Agra da Roca, which in Portuguese means- 'bay of rocks'. It was then renamed Bahia da Lagoa, which was changed to Algoa bay.

Algoa bay is a wide inlet along the South African, East Coast of the Cape of Good Hope. It is bounded in the west by Cape Recife and in the east by Cape Padrone. The bay is up to 436 m deep and the Harbour City, of Port Elizabeth is situated adjacent to the Bay. As is the new Coega deep water port facility. The metropolitan Municipality of Nelson Mandela Bay which includes Port Elizabeth, is located on the Western shore of Algoa Bay.

Joshua Slocum talks about Algoa Bay in his book 'Sailing Alone Around the World':

Geolocation
-33° 47' 35.0593", 25° 44' 23.5254"
References

New Dictionary of South African Place Names by Peter E Raper.

Wikipedia.

Joshua Slocum Sailing around the world.