How do you measure boat speed?

Boat speed is commonly measured using a device called a speedometer or a GPS unit. Traditional speedometers often use a paddle wheel or a pitot tube to measure water flow, while GPS units calculate speed based on the boat's position changes over time. Additionally, some sailors use knot meters, which provide speed in knots, a nautical measurement. Accurate measurements can be affected by factors like current and wind, so it's essential to consider these variables when assessing speed.