Twenty samples a season from the same twelve points, each with a temperature taken at the moment of collection. Point 7 reads between one point eight and two point four degrees below every other point, in every month, in every year.
I am an environmental protection officer for a coastal district and part of my season is bathing water.
The method is prescribed and I follow it exactly, because a sample taken any other way is not evidence.
Twenty samples a season, from May to September, at fixed points marked on a map that has not changed since 2009. You wade in to thigh depth, you fill the bottle thirty centimetres below the surface facing into the flow, you cap it under water, and you record the time, the state of the tide, the weather in the last twenty four hours and the water temperature.
The bottle goes to a laboratory on ice and comes back as a count of two bacteria. The temperature is mine, taken with a calibrated digital thermometer on a lead, and it goes on the sheet because bacteria behave differently at different temperatures and the number is needed to interpret the count.
Point 7 is two degrees colder.
Not once. Every sample I have taken there since 2016, which is a hundred and eighty something, in every month of every season.
The other eleven points on that beach agree with each other within about half a degree, which is what you would expect on four hundred metres of open sand, and they move together through the season the way the sea does.
Point 7 moves with them and sits two degrees below.
The equipment.
The thermometer is calibrated annually against a reference and I have the certificates.
I have used four different thermometers over the years and the third one was bought specifically because of this, and it is a better instrument than the department needs.
I have taken point 7 and point 6 within ninety seconds of each other, forty metres apart, with the same thermometer, more times than I can count. Two degrees.
I have taken point 7 with two thermometers at once, one in each hand. They agree with each other and disagree with the rest of the beach.
Where point 7 is.
It is a few metres east of the third groyne, in the middle of a bay of sand between two timber groynes, on a beach with no outfall, no stream, no spring line in the cliff behind it and no structure in the water.
I say that with confidence because the obvious answer to a cold spot is fresh water, and fresh water was the first thing everybody thought of.
The water company has confirmed there is no asset within eleven hundred metres. The council's own drainage map shows nothing. A survey in 2018 with a thermal camera from the promenade at low water found no seepage on that beach at all, which it would have, because groundwater coming out of sand at low tide is one of the easiest things a thermal camera can see.
And a fresh water plume would show in the salinity. I have taken salinity at point 7 nineteen times with a borrowed meter.
It is the same as the rest of the beach. To three decimal places, the water at point 7 is ordinary sea water at the wrong temperature.
The bacteria.
I have to put this in, because it is the part that made me go and read the file rather than just take the samples.
Point 7's counts are lower than the rest of the beach. Consistently, substantially, across nine years.
Colder water does hold bacteria differently and a two degree difference is real, but not this much. Point 7 comes back at a fraction of what the neighbouring points do, and in the two years when the beach failed its classification after a storm overflow, point 7 was inside the standard on days when everything either side of it was ten times over.
Which is the only good news in this and which is why nobody has ever queried it.
The extent.
In 2022 I did something outside my method and on my own time, which was to take a grid.
Forty temperatures across that bay at low water on a still morning, on a five metre grid, with the good thermometer, noted on a piece of paper on a clipboard.
It is not a plume and it is not a gradient off the groyne. It is a patch.
It is about eleven metres by seven, roughly oval, its long axis running out to sea, and the edge of it is sharp. Two steps and you are two degrees colder, and two steps back and you are not.
Point 7, chosen in 2009 by somebody who is now dead, off a map, at what was probably the middle of the bay, is inside it.
What I do.
I take the sample. I write the temperature on the sheet. The lab does the count and the count goes into the national data and the beach has held an excellent classification for six years, which is a thing this district is proud of and which the tourism people mention in print.
I have never written a line about the patch in any report and I am not going to, and my reason is that the classification is calculated from the samples, and the samples are taken at prescribed points, and point 7 is one of them.
Somebody moving that point forty metres east would be doing it for a good scientific reason and would also be lowering the beach's classification, and the beach would go from excellent to good, and the sign at the top of the ramp would change.
So I wade out to thigh depth at point 7 twenty times a season, and I fill the bottle facing into the flow, and I hold the thermometer under until it settles, which takes about eleven seconds, and I have never once got used to the temperature of that water around my legs.