Dene Stallard says three years ago his boat flipped on the water and he woke up in hospital.

If he runs into something, the boat might flip.

As rescue efforts proceeded, the Vietnamese boat flipped over and quickly sank.

Carbonell estimates that over the last eight years, there have been more than 10 accidents in which boats flipped or sank while racing there.

A newer alternative, the "sit-on-top," is open to the air, built of durable plastic, and floats in case the boat flips.

If you do the wrong thing through inattention and the boat flips, the rest of the eight-man crew will blame you.

Safety board officials immediately halted the test because of the threat the boat could flip.

Midway across the river, however, the second boat flipped.

Without ballast, the boat would flip over immediately and not be able to right itself.

Jena sat upright, attempting to jump clear and the boat had flipped over, dumping them both into open water between the two slabs of ice.