There are options for beach holidays in South Africa most notably in Kwa-Zulu Natal which has some wonderful warm water beaches such as those around iSimangaliso where whales can be sighted in October.
Durban's beaches are very popular and offer great surfing as well.
In the West there are some extremely scenic beaches such as Camp's Bay near Cape Town, South Africa's answer to St. Tropez.
Beaches along the Garden Route such as Buffel's Bay near Knysna and the whale watching area of Hermanus also offer great scenery although are not warm enough for year round swimming.