Sailfish watch from below as the snorkeler has gotten too close to the sardines and blocked the path of the sailfish. The sailfish will wait for him to back away before the attack the sardines again. Sailfish come to the waters outside Cancun to feed on sardines which are there feeding on plankton that is in the water during February. Sailfish, the fastest fish in the ocean, round up the sardines into bait balls and trap them against the surface. The sailfish then attack the sardines using their elongated upper bill to stun the sardines and feed on them one at a time.