The ebb and flow of the tides generally follows a sine curve, often described as the ‘rule of twelfths’. One twelfth of the volume of tidal water flows in the first hour after high water, two twelfths in the second hour, three in the third, three in the fourth, two in the fifth and the final twelfth in the sixth hour. In other words, it starts slowly, speeds up, and then slows down again before reversing for roughly the next six hours.
Susi Arnott and I swam along the coast from Cadgwith on the Lizard Peninsula in Cornwall, and placed a floating time-lapse camera in a gully to document a tide fall as dusk fell. The camera was left at the mercy of the tide, wind and waves with no human hand or eye to guide its compositions.
It seemed fitting to edit ‘Gully’, the resulting film, by the rule of twelfths. As the water flow increases the frames pass ever faster, before slowing into the dusk as we approach low tide.