Solo ocean racers do not sleep. They ration it. Twenty minutes at a time, sometimes less, spread across the whole twenty-four hour clock. The physiology behind this was mapped by a chronobiologist rather than a sailor. Human sleep runs in ultradian cycles of roughly ninety minutes, descending through light stages into slow-wave sleep before surfacing towards REM. Waking out of slow-wave sleep produces sleep inertia: a window of degraded reaction time and poor judgement that can last half an hour. A nap capped near twenty minutes usually ends before deep sleep consolidates. The sailor wakes functional. Claudio Stampi studied competitors through the BOC Challenge and the solo races that followed. His finding held. Racers who fragmented sleep into many short naps outperformed those taking fewer long ones on identical total hours. Daily totals often fell to four or five hours for weeks at a stretch. Nap length is set by geometry as much as by neurology. - A container ship makes twenty...