This is a Bonus Cache for the Meet the Claydons set of AdLabs. It's not hidden at the given location, but is within two miles of this spot. There's no need to visit/swim in Claydon Lakes and if you go to the given co-ords, you will just get very wet. No cache in the lake! A nostalgic spot for me though, and they do hovercraft racing here sometimes...
Nostalgia is a theme of these AdLabs and this Bonus cache. It was partly inspired by the time I had to stand for ages while being Joseph, for example. Please note, all locations - including the final for this cache - are available 24/7 apart from Claydon House which is open during usual trading hours. The footpath onto site gets close, but not close enough!
To find this cache, take the five sets of letters you've collected doing the above AdLab (they're also in the Journal entries for it) and rearrange them into a two-word phrase related to this cache and enter that into the Certitude link below. The correct code will give you the correct co-ords. All very simple!
Good luck and remember, you need to complete the AdLabs and crack the code to get the final co-ords for this cache!
You can validate your puzzle solution with certitude.