The length of one wave cycle is the wavelength. The wavelength can be measured as the distance from the top of one wave to the top of the next wave or from the bottom of one wave to the bottom of the next.

a sound wave showing frequency

You can also think of the wavelength as the distance that a sound wave travels in one cycle. Wavelength is related to the speed at which sound travels. You can calculate the wavelength of sound in seawater by dividing the speed of sound by the frequency of the sound:

Wavelength = Speed of sound / Frequency of sound

The speed of sound in seawater is the same for all frequencies. A high-frequency sound therefore has a shorter wavelength than a low-frequency sound. Using 1500 meters per second for the approximate speed of sound in seawater we find:

(Hertz, or cycles per second)
100 15
1000 1.5
10,000 0.15