A few knots are easy to misplace on sea trials. Conditions are rarely identical from one test to the next. Are the bottom and running gear clean? Are fuel, water and waste equal in weight? Is the owner’s stuff aboard? In addition to sea conditions, speed trials are about location, location, location. Due to a principle of fluid dynamics named for a fellow named Bernoulli, planing hulls in shallow water benefit from lift, while displacement hulls slow down. With luck, a boat might have one “perfect” sea trial: on launch day!