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RBYC Brighton Icebergers Sea Temperatures

Some all-year-round swimmers record their open-water swims at Royal Brighton Yacht Club (RBYC) on their smartwatches.  They use Garmin watches that also automatically sync up with Strava. We have an Icebergers activity group that those on strava can join which is at:

A few of these swimmers also authorise sharing their data at  We mostly monitor the changing sea temperatures and it also collects the swim distance. Below are some of the graphs from the swim temperatures recorded by the swimmers from June 2021 to June 2024.

For those swimmers using the service, here is a summary of their swim counts, distances and average distance from June 2022 to June 2024. Note that swimmers joined the service at different times.

You may note a couple of extraordinary regular swimmers in these recordings: Clive F and Fran J. These two swimmers will swim between 40 and 50 kilometres per month over the winter months. Remember in 2022, Fran clocked up 888 km swam during the year. Not all her swims are in the Brighton. But in the cold winter of June 2024, Fran swam 52 kilometres at Brighton and Clive’s distance was down to 31 Km because of overseas travel. Their winter swim distances in 2023 were 152 Km for Fran and 93 Km for Clive. The average temperatures for these swimmers over winter last year were 11.9c, 10.5c and 11.3c respectively, but that didn’t perturb them doing regular Yellow Pole swims. Their average winter swim distance is 1,750 & 1,638 respectively… Bravo!

Other notables in the recent recordings over winter are, Janie Z, Romney and Michael B. Janie, who did 60 km through the 2023 Winter. Now that Michael B has the correct watch, he’s eaten up 24 Km around Brighton over the last month of June 2024.

The Winter Big Course Challenge

Established Brighton Icebergers will be familiar with the Big Course Winter Challenge. A Big Course is slightly over 2 Km and takes 40 minutes to 1.5 hours depending on your swim speed and the conditions. In June it’s cold. In late July and August, it’s cold with stormy conditions and regular large waves from the South Westerlies. The Honour Board noted those who completed the most Big Course laps over the winter months in either July or August. It started at 6 laps by John Locco in Aug 2001 but Paul Percy topped 44 laps in Jul 2006. Only hardy insulated swimmers could endure this dangerous daily endeavour. Paul Percey did 100 Laps in the Winter of 2006, (Jun, July, August). He completed the 100 laps in 88 days. Hugh O’Connor threw down the gauntlet in the 2009 winter topping this with 105 laps in 53 days. This is well over 215 kilometres of sturdy 10c or 11c winter swimming in 3 months. Touché

  • WARNING: Cold water endurance swimming is very dangerous – do not attempt these feats without support, knowledge, sufficient training and exposure. You can read about hypothermia limits here.

Smart Watches vs Manual Readings

At RBYC Brighton the sea temperatures are also recorded manually by various temperature readers including David Tokin, Paul Maguire, late Doug Weir, late Billy Dodd and late Gary Liddell. These manual sea temperature recordings are taken in waist-height water off the beach. The smartwatch readings are taken as an average over the distance of the swim. It is usually warmer outside of the pier breakwater than inside the pier breakwater, which is shallower water. Compared to a larger body of sea water such as Port Phillip Bay, the shallower water is colder in the winter and warmer in the summer. From my swim measurements, there is often a 1-degree Celsius difference between outside the rocky breakwater and inside. Comparing the data from our manual readings and the smart watches over time, the variability between the beach manual measurements and the average smartwatch readings is +-0.7c, (the average difference depends on the season).

The great late Harry Raisbeck recorded sea temperatures at Brighton Baths for many years. During a clean-out, a travesty occurred and his studious recordings were thrown away. (If you know more details about this please contact me, we would love this not to be true). However, The Baths retained one year of his record keeping and framed his sea temperature records for 1988.

I’ve included Harry’s 1988 sea temperature readings at Brighton Baths with the RBYC Manual and Smart Watch Readings below.

What do you think? Do you have any questions? Do you do any local temperature recording? How do they compare? Let me know in the comments below.

Further, if you have a smartwatch with a thermometer and would like to collect your swim data on the service, then go to the and read How it Works and then contact John Scanlon with the Contact page.

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