The silvertip nudibranch is a tricky beast, existing in two species in Cape waters that are indistinguishable from one another unless you catch them in the act of laying eggs. The Cape silvertip nudibranch (Janolus capensis) lays a flat, spiral egg ribbon, while the medallion silvertip nudibranch (Janolus longidentatus) has a globular egg mass.

Silvertips can grow to about four centimetres in length, and like many local nudibranchs feed on bryzoans. Spotting them is not generally difficult as their colouration stands out quite a bit from the oranges and browns prevalent on reefs in Cape waters, but (again, as with many nudibranchs) learning what their favourite food looks like will assist you in searching in likely locations.

These nudibranchs are endemic (found only on) the eastern and western Cape coast of South Africa. If you want to know more, I recommend Nudibranchs of the Cape Peninsula and False Bay by Guido Zsilavecz.