Interesting idea. What if the wavelength is much longer than the
structure -does that have an effect?

Cheers

Bob Crantz wrote:

Actually, the rise and fall of water over a shallow plug or area does cause
a "suction" effect and will pull you toward it.

See for yourself, just watch the water over a shallowly submerged boarding
ladder, piling or rock. The structure truncates the wave structure
underneath the surface and only allows higher frequency components of the
wave to exist above the shallow, hence the faster waveforms in the water in
the decaying response waveform and the lower frequency components in the
forcing function. In other words, the water drains faster than it fills (or
has a different waveform) and a relative "vacuum" is formed.

BC