A "breach" or a "lunge" is a leap out of the water, also known as cresting. The distinction between the two is fairly arbitrary: cetacean researcher Hal Whitehead defines a breach as any leap in which at least 40% of the animal's body clears the water, and a lunge as a leap with less than 40% clearance. Qualitatively, a breach is a genuine jump with an intent to clear the water, whereas a lunge is the result of a fast upward-sloping swim that has caused the whale to clear the surface of the water unintentionally. This latter "lunging" behaviour is often a result of feeding in rorquals. The right, humpback, and sperm whales are the most widely observed jumpers. However other baleen whales such as fin, blue, minke, gray and sei whales also breach. Oceanic dolphins, including the orca, are very common breachers and are in fact capable of lifting themselves completely out of the water very easily, although there is little distinction between this and porpoising. Some non-cetacean marine creatures also exhibit breaching behavior, such as several shark species and rays of the genera "Manta" and "Mobula".