Ironically, the biggest fish in the sea is only interested in the smallest. As filter feeders, Whale Sharks swim with their mouths wide open, filtering huge amounts of water using their gill rakers to net plankton and other microorganisms. Whilst feeding during the day at the surface is usually passive, rarely prey such as krill gather in large swarms on the surface, and Whale Sharks charge chaotically through the krill balls at speed with surprising agility & speed.