Peggybetty, I was in S.A.5 years ago and with much difficulty got to Robben Island. At that time (maybe still)the only way to land on the Island was to go on the state ferry boat. Getting a ticket for the ONE trip per day is difficult, I dont remember why something like applying to the council the week before or queueing early as first come first served and there may be none left.
I went to the tourist office in town the day before and bought a ticket for a sunset champagne cruise and got a free ticket for the state ferry. Many people will try to sell you trips to the Island but remember they cannot land ONLY THE STATE FERRY CAN LAND PEOPLE, DON'T BE CONNED.I got my info from Lonely Planet