Well , while you at the Snake and Animal Park , you can book a ferry boat ride on the dam. Its very relaxing with absolutely beautiful scenary all around you. You got the Magaliesberg infront of you , the yacht club at the snake park and the houses on the cliffs of the mountains with speed boats and jet ski`s all over the dam.
You will need a car to get to the Dam. I doubt if there are any busses going there. The people that work in the area and don't have their own transport use mainly mini bus taxi's which is not advisable for tourists.
If you want to spend some time on the Dam wall you can park your car on the side, before the robot and walk onto the bridge. Nice views of the dam and the boats.
Well on the boat beverages and snacks are sold. Just a point of interest , there is lots of spiders on that boat. Its not like they gonna bite you or anything but look out where you put your hands.