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':
The early Portuguese navigators, endowed with patience, were more than sixty-nine years struggling to round this cape before they got as far as Algoa Bay, and there the crew mutinied. They landed on a small island, now called Santa Cruz, where they devoutly set up the cross, and swore they would cut the captain's throat if he attempted to sail farther. Beyond this they thought was the edge of the world, which they too believed was flat; and fearing that their ship would sail over the brink of it, they compelled Captain diaz, their commander, to retrace his course, all being only too glad to get home. A year later, we are told, Vasco da Gama sailed successfully round the "Cape of Storms," as the Cape of Good Hope was then called, and discovered Natal on Christmas or Natal day; hence the name. From this point the way to India was easy with the help of Arab and Indian fishermen.
New Dictionary of South African Place Names by Peter E Raper.
Joshua Slocum Sailing around the world.