Lost At Sea — Jonathan Neale

Orrie and Jack don't know much about sailing. One day they are basking on a beach in the Canary Islands where their mum has taken them on holiday. Two days later they board a small yacht, along with their little brother, their mother, and her new boyfriend, Skip, to sail across the Atlantic on a lark. Then Skip, the owner of Good Company, falls overboard. Something is wrong with their mother. She won't leave her cabin. Orrie and Jack are used to taking care of her, but now it is up to them to navigate the thirty-six-foot boat to Antigua safely.
Lost at Sea, written in the alternating voices of two very smart, funny, and real kids, tells the story of a family working through their problems. It is also an intense and gripping adventure at sea that will have readers on the edge of their seats to the very last page.