Duiker Island is the Hout Bay seal colony stop: a tiny rocky islet where the main draw is close Cape fur seal encounters over a shallow, kelp-fringed anchorage in the island's lee. The bottom is granite and rock rather than sand, so the underwater plan is simple and the wildlife does the heavy lifting. Expect a short boat transfer, cold water and a busy marine-tour setting. It suits calm-day snorkelling or an easy scuba stop, but the real constraints are swell, boat traffic and a need to keep the channel clear.