This swim cap by Bestway is shaped like a fish: two big eyes at the front, a little fin on top and a tail at the back. The cap is made of supple silicone that stretches over the head and then stays snugly around it.
Bestway makes the model in three colours: orange, pink and blue. You order one cap, and which of the three you receive is not fixed. Anyone counting on a particular colour is best keeping that in mind.
Bestway gives this model from 3 years. At swimming lessons a cap holds the hair together and out of the eyes, and among all the things in the changing room a child recognises its own fish straight away.
Small enough to disappear into any swimming bag and cheap enough to hand over as an extra, alongside a diving toy or a pair of goggles, for instance.