Wobble across the deck of a rocking boat and somebody is sure say it: Stare at the horizon to get your sea legs.

Turns out, there might be science behind that ancient mariner's advice. It all has to do with the motion of bodies, concludes a University of Minnesota researcher.

After years studying how and why people rock back and forth in different situations, kinesiology professor Thomas A. Stoffregen wanted to see how the rocking changed when people were on a surface that, essentially, did the rocking for them.

"People move differently on ships than they do on land. It takes time to make the adjustments -- time to get your sea legs; up to several days. What changes as we get our sea legs? How do we make the necessary adjustments?" Stoffregen said in an e-mail.

He found out the hard way, stepping aboard his first ocean vessel in 2007 to do "sea legs" tests. He got seasick for two or three days on most cruises and, stuck inside the ship doing research, had no horizon to stare it.

"It was utterly miserable," he said.

Most people rock back and forth a few tiny centimeters every 12 seconds or so. On land, they sway more when they look farther away. But on the ocean the reverse is true, Stoffregen said. It's counter-intuitive -- you'd expect to have to watch the motion of the ship to gain balance.

He thinks the stable horizon lets you differentiate between the rocking coming from your body and the rocking coming from the boat, getting them in sync, so to speak. Stoffregen plans to study the differentiation's role in people who become seasick.

From a half world away, Charleston skipper Brad Van Liew agreed. Van Liew was in port in New Zealand in the midst of the Velux 5 Oceans around-the-world sailboat race.

"I don't know how many times I have been on a boat and someone heads down below to make sandwiches, take a rest or even just use the head, and the next thing you know they are vomiting off the rail of the boat," he said.

"Fixing on a steady point in the distance does seem to help them."

Some people seem more susceptible than others, said Meaghan Van Liew, his wife. She gets dizzy and has to do the stare. But her husband, for instance, has never had a problem with it.

Reach Bo Petersen at 937-5744.