The humpback's pectoral fin is longer than that of all other species of whales, measuring one-third the whale's body length, or approximately twelve to fifteen feet. Humpbacks will often roll onto their side or back and slowly slap the water's surface with one fin or both fins simultaneously. The slapping of fins may serve as a communication signal to other whales.
12 January 2016 off of Kihei Boat Ramp.