One very hot sunny summers day on our annual Pembrokeshire holiday when our first child was about 8 years old, we all went to West Dale Bay. It was a perfect day with a calm sea and the tide coming in. The beach was not crowded with few people. We played with the children and had a picnic lunch. My wife had been swimming and afterwards lay down in the warm sun and went to sleep with our youngest child with her. My son and I were splashing about in the shallows doing nothing special. I was in about knee deep water when suddenly the sun went out. I immediately looked up to see what was happening in the cloudless sky. But there was no sky to see, instead a giant wave was hanging over us and descending down onto us. Without thinking I grabbed my sons arm and dived into the base of the wave, towing my son with me. There were second and third waves too that each also required diving beneath with my son gripped firmly by hand. Finally I found myself in normal sea water and hauled my son up alongside. He was coughing and spluttering and very angry with me. Why did you pull me under the water like that he wanted to know. He had not seen any of the big waves and I don’t think he really believed my story. We came ashore and went up to my wife who had missed everything and she did not really believe me. So we returned to normal beach activity. It was only some days later when reading the local newspaper that I learned that two fifty year old fishermen on a headland nearby had been swept off the rocks by a big rogue wave and drowned. So I was not the only one to experience the three big rogue waves. I must add that having lived in the tropics for most of my working life, the sea has always been my hobbie and I am at home in it and spent decades spear fishing in both the Caribbean and Red Sea and I am familiar with surf but warm surf.

I have heard of rogue waves but that was the only time in my life I experienced them. When I was a postgraduate at London University, one of my friends was doing a Ph.D. in the Outer Hebrides. He had been mapping there for several years and was coming to the end of the work. He told me a story about a rogue wave he experienced. He was out on the Atlantic coast finalising his precious map. He was above the beach on heather with the map spread out on a rock in front of him and his back was to the sea. As he made his delicate ink corrections to the map he heard the sea roaring behind him. He thought it was a big wave but as he was above the beach he did not pay any more attention. He said he was listening and the sound got louder and louder and it kept going on. Suddenly he and his map were immersed in surf as a great wave swept over them. He managed to save his map although it was damaged by the water but the data was not lost. It was a rogue wave but he had never heard of them before.

It may be that rogue waves get bigger the further north one goes. We have a family friend living in Shetland. She tells the story of some summer visitors who came with a car and caravan and camped one night in a field at the north end of her island not far from the sea. They, their car and caravan disappeared one night without trace and the mystery has never been solved. I can only think of a rogue wave.

There is also the famous story of the lighthouse on the tiny Flannan Isles. These are a group of rocks well out into the north Atlantic offshore of the Isle of Lewis in the Outer Hebrides. The three lighthouse keepers vanished completely in December 1900. A passing ship reported that the light, normally visible for 24 miles, was out. The support ship – the S.S. Hesperes – was sent out to investigate. The search revealed no sign of the men. Inside the lighthouse a chair was upturned, the beds unmade and a meal of cold meat and boiled potatoes lay untouched on the table. The last entry in the log was dated December 15th and revealed that the day before there had been a storm but it had died down. Perhaps the most significant observation was that the jetty was battered and the railings were twisted. Unfortunately for science it was reported that as the ship approached the jetty three cormorants were seen diving off the rocks. This gave rise magical myths and others including pirate raids, sea monsters and vengeful ghosts. Another important clue was provided by a woman living in the hamlet of Crowlista on the coast of Lewis (Outer Hebrides) near Uig and opposite the Flannan Isles, who on 15th December was hanging out her washing when she saw a massive wall of water approaching from the west. She ran back inside the house and secured the doors and windows. A vast wave hit the shore and happily only her washing and the washing line were carried away. Today the most logical explanation is that the lighthouse was hit by a rogue wave just before lunch and one of the lighthouse keepers ran out to assist the other two and all were swept out to sea.

So what makes a rogue wave. It is not a storm at sea as that will generate a swell that can last for days. It has to be something like movement on a submarine fault that displaces the sea bed. Recently with improved satellite television communications and especially mobile phones with video facilities, the world is becoming familiar with filmed records of tsunamis following big submarine earthquakes where the sea bed is displaced a meter or a few meters along active geological faults. It seems rogue waves are most likely tsunamis which can traverse oceans. Earthquakes on one side of the Pacific Ocean can today trigger tsunami warnings on the opposite side of that vast ocean. Recent studies in California by geologists are recognising deposits from prehistoric tsunamis that have washed over land 600 feet high. The three rogue waves we encountered on West Dale beach were extremely small. I was standing in knee deep water and the breaking wave was well over my head giving it a height of no more than six or seven feet before it broke over us. Happily they are extremely rare with only one instance encountered by us in fifty years of Pembrokeshire summer holidays.