What effect does the bottom drag have on a wave as it approaches the shore?

As waves approach the shore, they interact with the ocean bottom due to friction and the drag caused by the seabed, which has significant effects on their characteristics. The bottom drag slows the wave down, particularly impacting the wave's speed. As the wave slows, its energy is transferred forward, causing the wave height to increase as it becomes steeper, and the wavelength decreases. This happens because the wave's energy is concentrated in a smaller horizontal distance as the wave height rises.

Thus, the correct understanding of this phenomenon explains how the wave height increases due to the accumulation of energy at the top of the wave, while simultaneously, the shortening of the wavelength results from the lower speed at which the wave moves as it interacts with the ocean bottom. This relationship between wave height and wavelength is intrinsic to the physics of wave behavior in shallow water, making the response that describes a decrease in wavelength alongside an increase in wave height entirely accurate.