"'We experienced a total of 4 knockdowns," Watson wrote in her blog. "The second was the most severe, with the mast being pushed 180 degrees in to the water. Actually pushed isn't the right word, it would be more accurate to say that Ella's Pink Lady [Watson's yacht] was picked up, thrown down a wave, then forced under a mountain of breaking water and violently turned upside down."
Just last summer, Sunderland's older brother Zac set the world record for being the first person under age 18 to circumnavigate the globe solo in a sailboat.
His record was eclipsed a few months later by British teenager Mike Perham, who is a few months his junior.
ABC News' Bert Rudman contributed to this report.