The bus leaves from the V&A Waterfront, just outside the aquarium. As you can see from the front of the bus, this is the "Blue Mini Peninsula Tour" which basically traverses the city, takes a drive over Kloof Nek, down to Camps Bay, and along the coast back towards Sea Point, ending back where you started at the V&A Waterfront.
Do this trip if you have half a day available of if you'd prefer to spend a long time at hop-off spots - you're sure to enjoy it. As an alternative you could take the day-long tour that goes via Kirstenbosch Botanical Gardens, over to Hout Bay, and back along the coast past Camps Bay, Sea Point, also returning to the V&A Waterfront.