Earth without land masses would have around 0.5m to 1.5m of tides, depending if it is springs or neaps. All the higher amplitude tides are caused by resonance i

Earth without land masses would have around 0.5m to 1.5m of tides, depending if it is springs or neaps. All the higher amplitude tides are caused by resonance in the sea. The North Sea and the Channel and Irish straight are quite resonant.