with a narrower shelf, there is still a resonance but it is mismatched to the frequency of the tides and so has less effect on tidal amplitudes. however the effect is still enough to partly explain why tides along a coast lying behind a continental shelf are often higher than at offshore islands in the deep ocean (one of the additional partly explanations being green's law). resonances also generate strong tidal currents and it is the turbulence caused by the currents which is responsible for the large amount of tidal energy dissipated in such regions.