Which term describes waves increasing height as they move into shallower water?

• A. Slack water
• B. Rip current recognition
• C. Wave shoaling
• D. Wave refraction

Answer: (C)

As waves move into shallower water, their height increases because the wave has less depth to move through, which slows the wave and compresses its energy into a shorter front. In deeper water the wave travels faster with a longer wavelength, spreading the energy out. When depth decreases, the wave celerity drops and the wavelength shortens, so the energy remains the same but is concentrated into a smaller space, causing the crest to rise. This process is called shoaling. It explains why kayakers feel steeper, taller waves as they approach shore, often leading to breaking near the shoreline.

Slack water isn’t about wave height change; it refers to periods of little current. Rip current recognition deals with identifying dangerous alongshore currents, not height changes. Wave refraction describes how waves bend due to different depths, which affects direction more than height.