These pictures (of St Brides Bay, Pembrokeshire) are taken on a falling tide.
The second is taken in exactly the same position, 2’40” after the first. In between, the water level rose gradually (the waves are very small – this is not an effect caused by one huge wave). Over the next 2 – 3 minutes the water dropped back as if someone had pulled the plug out. This pattern – significant variations in the water level, sort of “mini tides” – continued on a 2/3 minute cycle.