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Spring tides: When the sun, moon and earth are in a line and so there is a new or full moon, the gravitational pull of the sun on the earth’s water adds to the gravitational pull on the water by the moon. This causes the water on the earth to bulge outwards towards the sun and moon. As the earth rotates, the bulge, locked towards the sun and moon, appears to sweep around the earth in the form of a long-period wave. We get the highest high tides and the lowest low tides, and the tidal flow each way is strong. Spring tides are nothing to do with spring or the seasons – they occur naturally twice each lunar month, all year long.

Neap tides: When the sun and the moon are at right angles to each other respective to the earth, the bulge of the ocean caused by the sun is partially cancelled out by the bulge of the ocean caused by the moon. We get weaker neap tides – with lower high tides and higher low tides. The tidal flow, and its rise and fall, are not as extreme as with spring tides – and just like spring tides, neap tides occur twice a lunar month, all year long.