Clevedon Marine Lake is an unusual swimming pool on the Somerset coast. Every spring tide, the pool fills with seawater from the Bristol Channel. You swim alongside open views across the channel – a unique experience! The lake is open 24/7 and is managed by a community group. They rely on donations so don't forget to put a few coins in the white boxes by the lake or donate online.
The lake is open to swimmers, SUPs and canoers. You can bring along your inflatables too. For more information, see: clevedonmarinelake.co.uk
I found the route along the water to be the most beautiful. The lap went well. For the most part the path is on roads/footpaths and there are a few meters up and down, but everything is doable.
There is also a route that leads along the water to the right of the pier, but I haven't tried it.