Waves begin to "feel bottom" when the depth of water is

Equal to one-half the wavelength is the right answer.  

Water is regulated by many approaches such as depth gauges (based on force) a sounding line and by sonar range. Prior to the modern era, sailors would cast metal weighted materials into the ocean. Submarines made a new demand for depth estimation, to need to know the depth of boats in the water. However, waves start to "feel bottom" when the depth of water is equivalent to one-half the wavelength. As the wave approaches a lightweight bank, its track is adjusted. This involution made the tides to become inactive. As the flow becomes steeper, the width of the wave diminishes.

grav forces affect all objects magnetic forces affect magnetic objects and electric currents

i believe the answer is a hope it and is correct