Freshwater is often the stage on which millions of animals gather to find a mate, and the cycle of freshwater is the trigger for spectacular mating rituals and fierce competition. The start of the rains in South Africa brings about a violent battle between male giant African bullfrogs, while rare, hooded grebes in Patagonia perform one of nature's more comical dances to seduce their partner and a male cichlid fish builds a home for his harem from old snail shells. Narrated by David Attenborough