Congratulations, once again, to the organisers of the River Arun 3.8k swim which is always a great event.
All was not the same on the gadget or goggle front.
Today I had 4 devices that I wanted to do an open water GPS test for but I was limited by only having two arms. The Suunto 5, Garmin 945, Polar Vantage titan and Coros Vertix were all contenders for the honour of close contact with my Huub Archimedes III 3:5 wetsuit for 3.8k of splashing however I wanted to ensure that I had two awesome GPS tracks as this race is a once a year thing (kinda like most races in that respect). I’d seen DCR’s Garmin MARQ gadget GPS fail at his recent triathlon and had experienced a couple of similar fails myself recently too.
So…”What to do?”.
A: Testing of course
Yes. I did some testing during the week around Shepperton lake and all was good. Here are the results of that test of 2 separate laps with 2 watches per lap. I did a bit of running (5K in fact) and left that track on the image just because it looks a bit like Australia. I thought you’d like that?

So, they’re all pretty good right? I think they are all fully acceptable and you can see that I also started each lap from my car in the car park just to be double sure that a really full GPS signal was obtained. #PerfectTest.
RACE DAY: I decided to go to Arun with the Polar Vantage V Titan and the Garmin 945 (Review) just because I really like different aspects of both those watches.
Cutting to the chase, here are the results and you can probably make out that I turned on the watches and started recording in the car park before the 5-minute walk to the start line.
RESULTS: The Garmin and Polar both recorded a full race of data…but without GPS. The Garmin picked up GPS at the finish but the Polar did not. I stopped recording on both fairly quickly.
My friends in the real world know that I do swear more than occasionally and yet, my regular reader will know that I do NOT swear on this blog. However, this is one of those occasions where I am really, really, really, really, really, really, really tempted to swear. Did I say ‘REALLY TEMPTED’?
The Cause: The problem looks like when a signal is properly LOST that the watches do not try to recover. What was happening here, I think, is that: I was in an earlier loading/seeding wave (mass start) which meant that I was one of the first in the water but had to wait for the start gun. I was waiting 5-10 minutes, splashing around with the watch almost entirely submerged.
How to avoid: Well I don’t know exactly how to avoid this but my suggestion would be to 1) get an initial fix (soak) at your race location then 2) stop recording. Only start recording when the race actually starts as there MIGHT be a period near the start when your watch tries harder to get an maintain a GPS fix.
Perhaps this post could have been entitled: Why your triathlon watch might not have been tested for deepwater race starts
Note: I have also had this with the Suunto 5 and all those 3 devices share the same Sony GPS chip. I’ve not had the problem with the Vertix, although I haven’t done many OWS workouts with it yet.
Oh yes, my Zoggs Predator Flex goggles leaked too and they’re fairly new and were fairly tight and clean.
Here are the Suunto 9 and Coros PACE from 2018…#PerfectInComparison