The daggerboard is a type of keel beneath the boat that allows the boat to sail at an angle into the wind.

UNESCO: Race for Water victim of ocean pollution

Henry recalls the screechings of their little boat as its keel scraped along the riverbed earlier that morning, and he wonders, briefly, if he was meant to heed these sounds as a warning.

NPR: Excerpt: 'Woodsburner'

Most America's cup boats throughout history, including the 2010 versions, were traditional monohulled boats that had a keel: a giant, underwater fin that counterbalances the boat against the wind.

WSJ: Before America's Cup Capsize, Concerns About Safety

The tough race sees boats battling against the prevailing wind and encountering huge seas, which this year caused two dismastings and one boat, Cheminees Poujoulat-Armor Lux, to lose its keel.

BBC: Desjoyeaux crossed the Atlantic in eight days eight hours