SF Fig. 4.4. Depiction of a method for estimating wave height from a known object in the water
Image by Byron Inouye
Whether you are a surfer, a boater, or a casual observer, being able to tell how big a wave is can be very important. There are two simple ways to estimate the height of the surf.
Judge the relative height of the waves as compared to a surfer, a boat in the water, or some other reference. For example, if a surfer appears as tall as your thumb and the surf appears twice as tall as your thumb, then the wave is about twice the surfer's height (SF Fig. 4.4).
SF Fig. 4.4. Depiction of a method for estimating wave height from a known object in the water Image by Byron Inouye
If it is safe to do so, the size of the wave can be estimated by walking down the slope of a beach until the top of the breaking wave and the distant horizon are aligned. When the wave and horizon are aligned, the vertical distance from eye level to sea level, or the level of the water returning to the sea, is about the height of the wave (SF Fig. 4.5).
SF Fig. 4.5. Depiction of a method for estimating wave height by knowing your height above sea level Image by Byron Inouye