Many people have witnessed individual basking sharks leaping from the water. This behaviour is not fully understood, but some believe that the shark may be trying to get rid of parasites or commensals such as remoras and sea lampreys, which are often seen attached to the skin of the basking shark. The lamprey cannot cut through the denticle-armored skin, but they may be enough of an irritant to cause a reaction like jumping or rubbing against an object to get rid of them. The cookiecutter shark has also been known to attack basking sharks by using its suction cup-like lips and muscular pharynx to drill off pieces of flesh on the outside of the shark.