  We show that significant water wave amplification is obtained in a water
resonator consisting of two spatially separated patches of small-amplitude
sinusoidal corrugations on an otherwise flat seabed. The corrugations reflect
the incident waves according to the so-called Bragg reflection mechanism, and
the distance between the two sets controls whether the trapped reflected waves
experience constructive or destructive interference within the resonator. The
resulting amplification or suppression is enhanced with increasing number of
ripples, and is most effective for specific resonator lengths and at the Bragg
frequency, which is determined by the corrugation period. Our analysis draws on
the analogous mechanism that occurs between two partially reflecting mirrors in
optics, a phenomenon named after its discoverers Charles Fabry and Alfred
Perot.
