In a truly mesmerising short film by Maxwel Hohn, he shows the daily journey of western toad tadpoles through a lake in British Columbia. They all move as one across the bottom of the lake as a kind of carpet, so they can reach the more oxygen-rich and warmer shallow waters, and then they all move back to the deepths later in the day.
Metamorphosis is something that my brain can't quite get to grips with. Gradual evolution caused by natural selection I understand. But these tadpoles transform within a number of weeks!