Chiisana Eiyuu: Kani to Tamago to Toumei Ningen EP1 - Kanini & Kanino

Two crab brothers embark on a grand underwater adventure to find their father, after an accident carries him far downstream. Depicted as tiny beings in a large and merciless natural world, the brothers must evade a series of freshwater predators if they are ever to reunite with their family again.