Once, many years ago, I was rowing across Wexford Harbour when I was caught in a tide rip that almost pulled my boat out into the Irish Sea and away from any rescue. Fortunately, I had learnt to row across the flow and not against it and, after a long and exhausting pull, the tide turned and I finally made it to safety. Since then, I have had a healthy respect for the tide and love to watch it ebb and flow.
The turn of the tide is one of those immutable things in life. Like night following day, summer fading to autumn, middle age after youth, I know it will always come. I cannot stop its steady progress. It never lets me down. Ebb and flow, fall and rise, twice a day, unfailing, dependable, predictable. It carries my boat along or stops it in its tracks. It pushes up the beach, slowly erasing my footprints. It leaves behind rich offerings. A spiny spider crab that once crept about the deep seabed, a heap of oyster shells dredged from the sandbanks offshore or the bleached skull of a seabird that did not survive the winter.
Anyone who follows the tides closely knows that they are connected to the monthly cycles of the moon. A full moon and a new moon coincide with the highest (spring) tides while lowest (neaps) tides are during the periods of waning (decreasing) and waxing (increasing) moon. These are ancient terms, dating from the earliest days of sailing boats and still used by modern seafarers. The writer Adam Nicolson said, in his book The Sea is Not Made of Water, “no wonder people could think the tide in some way inanimate, motivated not simply by mechanical action but by some hidden, purposeful being, beyond our understanding”.
The tide is my constant friend, not a threatening adversary
So important are the tides to seafarers that annual tables are produced giving the times of high and low tides each day, the maximum height of the seawater and the variations for different ports. The spring tides occur twice each month and, if accompanied by low pressure and strong onshore winds, can cause significant coastal erosion and flooding. As well as moving up and down, the tide also flows along the coast most strongly around headlands and through narrow gaps such as the sounds between islands and the mainland. Tidal stream atlases give the figures for different parts of the coast allowing a calculation of the effects on speed of a boat.
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The tides are also important for wild creatures, especially those that spend most of their lives on the seashore. In rock pools, the crabs, shrimps and mussels have to adapt to regular wetting and drying each day, restricting their feeding times to when the sea carries plankton into their path. Wading birds can only feed during low tide periods when the shellfish and worms buried in the sand are accessible to their long beaks. When the estuary fills with seawater they must retreat to roost in large flocks on safe places like islands, piers and offshore rocks.
When the tide turns against the wind direction, it pushes the sea surface up into small crests that change the motion of a sailing boat, like driving from the road on to a gravel track. Just as the wind moves the air about, tides pull and push seawater around the coast, in and out of rock pools, up and down the beach. But unlike the wind, which is invisible, unpredictable, sometimes gentle, often angry, I can see the tide as it passes, watch its steady progress, make allowances for its effects.
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The turn of the tide is a wondrous thing. The constant movement of the oceans pauses for a moment, takes a deep breath, reaches its limits and starts to return the way it came. Curtains of seaweed are swept in the opposite direction, sand grains roll down the beach and crabs scuttle into deeper water. I feel a different pull on the boat as it implores me to follow rather than resist it. The tide is my constant friend, not a threatening adversary. But I have reached this accommodation after 60 years of experiencing the sea. After that close shave in Wexford Harbour, it seemed like the tide had granted me a reprieve and taught me a lesson for the future.
Richard Nairn is an ecologist and writer. His most recent book Wild Shores is published by Gill Books