The oceanic whitetip shark is mainly solitary and swims slowly, and is usually seen cruising near the top of the water column, covering large amounts of empty water, searching for prey or any food source. Until the 16th century, sharks were known to mariners as "sea dogs". The oceanic whitetip shark, the most common ship-following shark, shows dog-like behaviour when it is attracted by something which appears to be food. It starts swimming greedily towards the food source, approaches cautiously but stubbornly. It keeps a safe distance if driven off, but is ready to rush in if the opportunity presents itself. Oceanic whitetip sharks are not fast swimmers, but they are capable of surprising bursts of speed. They commonly compete for food with silky sharks, often presenting aggressive displays. There does not seem to be segregation by gender and size. Oceanic whitetip sharks usually follow schools of tuna or squid, and trail groups of dolphins and pilot whales, scavenging their prey.