Phytoplankton are microscopic algae, which multiply with such amazing speed they produce more annual growth than all the plants on land put together. The immense bloom of phytoplankton spreads across the oceans and provides food for many creatures. One of those which benefits is the common jellyfish. These tiny polyps may look like anemones, but they are actually baby common jellyfish. Each separates from the stack of polyps and swims away. Eventually they will grow up and form huge swarms.