Deep down in the sea, a tiny coral planula looks for a place to settle. It lands on a rock and soon has more and more family to build up coral. They meet various creatures in the water world - drifting jellyfish, fish in different sizes and colors and even strange-looking fish. But one day, as dark rain and things begin to fall down into the ocean, the water gets warmer and warmer. The planula family turns white and two planulae have to leave their old place looking for a new home.