Until the 16th century , sharks were known to mariners as `` sea dogs '' and the oceanic whitetip , the most common ship-following shark , exhibits dog-like behavior when its interest is piqued : when attracted to something that appears to be food , its movements become more avid and it will approach cautiously but stubbornly , retreating and maintaining a safe distance if driven off , but ready to rush in if the opportunity presents itself .
Until the 16th century , sharks were known to mariners as `` sea dogs '' , and the Oceanic whitetip shark , the most common ship-following shark , shows dog-like behavior when it is attracted by something which appears to be food ; it starts swimming greedily towards the food source , and will approach cautiously but stubbornly , retreating and keeping a safe distance if driven off , but ready to rush in if the opportunity presents itself .