Answer: when wavelength is long frequency is low, when wavelength is short frequency is high.
Step-by-step explanation:
When the known distance between the wave crests is large ( e.g, then the wavelength is long), this makes the boat bobs up and down movement to reduce resulting in ( the frequency been low). When the known distance is small ( e.g. the wavelength is short), then the boat bobs up and down movement increase which translates to an increase ( the frequency is high).