All of which should make his Tide Walk event at Edinburgh’s Portobello Beach on Friday well worth attending. For the last couple of months, Thomson and his young family have been slowly working their way around the British coastline in a camper van, starting in St Ives in Cornwall and passing through Dartmouth, Brighton and Whitstable. At each stop, Thomson has been hosting guided beach walks during which he introduces paying punters to the science behind tides and also gives them practical tips on how to apply their new-found knowledge.
“The idea is we walk for a mile along the beach and we stop every 200m or so,” he says. “We start off with the basics – how tides work. They are these waves that flow all along the coastline, and I’ve got a rope I use which really clearly demonstrates this: if you flick a rope and you imagine all the bulges in it, that’s how the tide travels along the coast.
“After that, every stop builds on what we spoke about at the last one, so we go on to talk about how the moon affects the tide, how weather affects it, and then about how waves are formed and how rip currents are formed.
“So we do talk about the general theory, but then we’re constantly applying it back to where we are at that place and how the specific coastline where we are fits in with the theoretical notions of what’s happening.”
Thomson graduated from Newcastle University with a BA in Architecture in 2010 (also learning to surf at nearby Tynemouth between lectures), and he subsequently set up a bespoke furniture workshop in Deal in Kent. He also joined the Deal lifeboat crew, and it was there that he started to become fascinated with the way tides worked. Soon he began to design tidal maps – first for Deal, and then, as commissions started pinging in, for beaches and seaside towns all over the world. In 2015 he made a camper van circumnavigation of the British Isles with his partner Naomi and their six-month-old daughter Ottilie, and it was this adventure that formed the basis for The Book of Tides. Last year he published the follow-up, The World of Tides, which takes in everything from whirlpools in the Arctic to the monster waves of Nazarré in Portugal.
Thomson’s books are specific enough to be of use to experienced water users, but they also appeal to people with a general interest in the sea, and it seems his Tide Walk events this summer have been attracting a similarly mixed audience.
“About 90 per cent of the people who come are people who use the water,” he says. “I reckon 50 per cent of those people are swimmers and then you’ve got some surfers and a few kayakers. And then there are some people – about 10 per cent – who are just interested.
“I get a lot of families, too,” he continues. “Sometimes you get three generations – that’s nice because it appeals to them all in a different way. A lot of it is to do with the safety aspect – how to go out and enjoy the sea safely, what to do when you’re caught in a rip current, things like that.”
As the Valves sang back in the 1970s, there ain’t no surf in Portobello (well, except very occasionally on a monster north-easterly swell) and as a result there aren’t usually any rips, but Thomson will have plenty of other things to talk about.
“On a waveless beach, most of it is about the tidal currents,” he says, “so if you’re going out in your kayak when the currents are flowing at their maximum speed to the west, you’re going to get pulled along at three or four miles per hour, and if it’s quite windy it can be quite difficult to make headway against that. So if you want to go a certain way you need to time it for when those currents are running the right way for you.”
William Thomson’s next Tide Walk is at Portobello Beach in Edinburgh on 3 August, for details visit www.tidalcompass.com