The behaviour is mechanically specific. The dolphin begins rotating below the surface, where water resistance is high and torque can be generated by the tail and flippers. As the body leaves the water the resistance vanishes, so the rotation already established carries on almost unchecked. Rotation rates observed in Hawaii exceed seven turns per second in the fastest leaps, with up to seven revolutions in a single jump.
The re-entry is untidy by design, throwing a loud splash. Kenneth Norris, who studied Hawaiian spinners for decades, proposed that both the noise and the impact matter: the sound may serve as an acoustic signal within a spread-out group, and the impact may dislodge remoras clinging to the skin.
Neither explanation is settled. Remoras are sometimes seen leaving spinning animals, but no study has shown the spin is chiefly for that. Acoustic signalling, play and social coordination remain competing accounts.