Physicists explain how to execute a nearly splashless dive

Olympic divers slice into a pool with a quick turn underwater that minimizes splash. But not for the reasons many athletes think it does, according to research reported November 20 at a meeting of the American Physical Society’s Division of Fluid Dynamics in Indianapolis.

“The way that divers describe it,” says fluid mechanics researcher Elizabeth Gregorio of George Washington University in Washington, D.C., “is that they want to pull the splash in with them.” The goal is a nearly splashless rip entry that Gregorio says makes a sound resembling tearing paper.

To study the move, Gregorio duplicated it with hinged models that bend in the middle, much as a diver bends at the hips. She plunged the models into water to simulate divers in action.

Angles cut into the model re-created the shape of a diver’s head and arms. The shape meant the model folded in the middle, just as the angle of a diver’s arms and head after entering the water helps the athlete bend at the hips to execute a submerged turn.

The folded model pulled air behind it to create a large, air-filled cavity under the water. It’s the same thing that happens when a diver turns underwater following a dive.

The effect, Gregorio says, “reduces the jets that would come up after you enter the water,” leading to a score-boosting rip entry. Instead of “pulling the splash in,” the air-filled cavity prevents the splash from forming in the first place.

The research isn’t all about divers’ technique. Gregorio wonders if rip entries reduce the forces divers experience on impact. If so, the studies could help with splashdowns for returning space missions. She also imagines stealthy drones that slip into water without leaving attention-grabbing splashes behind.