Complex sentence: In October, 2003, Miller's monohull yacht, the Mari-Cha IV, set a new world record, becoming the first monohull ever to cross the Atlantic Ocean in under seven days.
Split into simpler sentences: In October, 2003, Miller's monohull yacht, the Mari-Cha IV, set a new world record for crossing the Atlantic. It was also the first monohull ever to cross the Atlantic Ocean in under seven days.