A Little Fish in Deep Water (1996)

Lake Tanganyika is an 'Ocean' in Africa. Millions of years ago it was colonized by a little fish called 'Cichlid'. Otters, crocodiles, cobras and cormorants all hunt the fish in clear water. How the Cichlid survived and evolved is an incredible story for, millions of years later, there are over 200 new species - all found only in Lake Tanganyika. Incredibly, they have evolved to look like coral reef fish. There are cichlid equivalents of tuna, snapper, gobies and goatfish. They have evolved bizarre methods of breeding with mouth-incubation, lekking and, unique amongst fish, there is even a cuckoo. Despite all their specialization over millions of years, if an opportunity presents itself, the little fish can behave like their unspecialized ancestor. In the climax of the film, they bang together to feast on a hatch of sardine fry. This is the story of how one little fish has conquered a lake.

Unfortunately the movie A Little Fish in Deep Water is not yet available on HBO Max.