Rogue waves are the most threatening and beautiful monsters of the ocean. Reaching heights of 100 feet or more, these mammoth waves are deadly, hard to predict, and more common than once thought. <P> "I always tell people dinosaurs are dead, but big waves aren't," said Susan Casey, author of "The Wave." "To see a wave [that] is eighty or a hundred feet and be out in those waves, it's like being amongst the dinosaurs."

In her new book, Casey set out to study rogue waves -- a phenomenon which seem to defy physics. "For the longest time no one even knew they're out there. They'd been rumored to exist, but nobody believes those stories," says Casey. "Science still doesn't really explain it. The linear physics doesn't explain it. Quantum physics goes part-way towards explaining it, but not totally."

Every week, ships disappear in the ocean without a trace, and they're not just recreational vessels, according to Casey's research. Large freighters are actually consumed by the ocean a couple of times each month.

The Iranian oil tanker Tochal had its entire bow section torn off by giant waves in the Agulhas Current, off South Africa's southeastern coast.

For her research, Casey enlisted the help of those most familiar with rogue waves -- big-wave surfers, who often risk their lives to conquer some of the ocean's most dangerous waves. Extreme surfer Laird Hamilton, who has surfed waves larger than 100 feet, is a leader in the sport. "The conditions give you a certain power and a certain strength that you would [not] have if they weren't there," Hamilton, 46, told ABC News' Bob Woodruff.

Casey, a former member of the Canadian national swim team, went with Hamilton into waters normally off-limits to amateurs. "Laird knows about waves, you know the way birds know about the sky. That's his element. And I wanted to visit it. So I needed him to take me in there," she said.

Professional surfer Ian Walsh rides a wave off the shore of Tahiti in November 2007. Photographer Tony Harrington captures the ride.

Big-wave surfers seek out these ship-swallowing waves -- even in the most severe conditions. Here, extreme surfer Garrett McNamara barely escapes a wave's dark jaws.

In December 2009, when a super-typhoon spiraled across the Pacific, closing all harbors and beaches in Kalama, Hawaii, Laird Hamilton headed to the water to ride some of the biggest waves.

Perhaps, the ultimate adrenaline rush, surf this big is always risky. "I've had stitches and broken bones, punctured cheeks, a scalped head," Laird said.