Career
Van der Merwe was a quarter-finalist in the juniors events at the 1978 United States Open and 1979 Wimbledon Championships. In 1982, van der Merwe had his best season on tour. He reached the quarter-finals in Metz and was a doubles runner-up in the United States. Pro Tennis Championships, partnering Freddie Sauer.
The South African made it to the third round in the 1982 United States Open, with wins over Derek Tarr and Raúl Ramírez, before losing to Bob Lutz in four sets.
In Wimbledon he started the tournament by defeating Terry Moor and then lost a marathon second round match to Steve Denton. His match against Denton had to be stopped due to darkness, with the scores level at 10-10 in the fifth set.
When play resumed the following day, Denton finished on top, 13-11. While in Ireland, where he was working as a medical doctor, Van der Merwe was found dead in his car.
The cause of death is still unknown, although he had apparently suffered from high blood pressure in the time preceding his death.
Doubles: (1).