Speedo style swimwear is very common in South Africa given that it is a very sunny country with a great swimming history where speedo is a required suit for school swimming for boys/teens and competition. Small suits, cheeky and thong style for women are common on most beaches. It is true that many beaches are more conservative and board shorts on guys are very common (surfing). You won’t have a problem with a speedo style suit at most beaches. I’ve worn smaller style bikini or tanga suits at a lot of beaches in South Africa. The more remote or deserted the beaches are the smaller you can go with your suit. At some you can even get away with being naked to tan. I don’t have very much experience with the dolphin coast of Kwa Zulu Natal but I would say that if there is a lifeguard at the beach (quite commonplace) that you should ask them and see what they say or ask which beach you could go to to wear a thong suit (or to go naked). The seas along the coast near Durban can be quite wild with lots of rips and large waves with undertow so be careful if you do venture into the sea and take local advice seriously. Happy to answer other questions you may have if you want to PM me.

This is great information. Thank you I am planning to bring both swim briefs and swim thongs. I will break the seal on the thongs in more remote areas with my wife and then go from there.