An amphidromic point is an area in which the amplitude of the tide is close to zero.
Amphidromic points are caused by resonance phenomena that occur in some oceanic basins. The tidal wave of these basins turns around an area where the tidal wave is stationary: the amphidromic point.
An ocean map of amphidromic points. The points where the tide is zero are located at the intersection of the white lines. © NASA / Goddard Space Flight Center, Jet Propulsion Laboratory, Topex/Poseidon
Amphidromic point - 1 Photo