Engineers and physicists at the Australian National University (ANU) have built a tractor beam.

The rig uses controlled waves to moves objects floating about on water, and could provide a radical new way to confine oil spills, manipulate floating objects and investigate rips at the beach.

The ANU team has found that they can control water flow with simple wave generators, which enables them to re-direct floating objects at will.

“We have figured out a way of creating waves that can force a floating object to move against the direction of the wave,” said research leader Dr Horst Punzmann.

“No one could have guessed this result.”

Starting with a ping-pong ball in a wave tank, the group calculated what size and frequency of the waves would be needed to move the ball.

High-tech particle tracking tools showed that the waves actually generate small currents on the surface of the water.

“We found that above a certain height, these complex three-dimensional waves generate flow patterns on the surface of the water,” ANU researcher Professor Michael Shats said.

“The tractor beam is just one of the patterns, they can be inward flows, outward flows or vortices.”

Interestingly, the team says there is no mathematical theory to explain the movements on the surface.

“It's one of the great unresolved problems, yet anyone in the bathtub can reproduce it. We were very surprised no one had described it before,” Dr Punzmann said.

The research has been published in the journal Nature Physics.