It's rather warm outside (32.6°C or 91 F) and I'd like to go for a swim. Having lived in The Netherlands and Sweden, I'm used to living near lakes and the fact that any surface water is by default open to swim in (unless a nature reserve or industrial site), but I have a hard time finding those in the UK. Looking at places near me on wildswim.com, one says Open Water Swimming Sessions can only take place during supervised sessions run by the Activity Centre. No swimming is to take place other then through and organised session., another has specific opening hours. Both make no sense at all for wild swimming, so now I'm rather confused. I also found this list but it's incredibly short for a country the size of the UK (NB: the aforementoined link is currently misconfigured which may trigger security warnings, but lists to a dozen or so popular public lake beaches within the UK)
There's plenty of surface water near me, and I'd like to take a dip and cool off. I don't care for changing rooms, safety buoys, or supervision (but I'd appreciate not to have to wade through 3-metre high stinging nettles to reach a lakeshore). If I identify a pond, lake, canal, or river, how would I tell whether swimming is permitted there? Is it permitted unless explicitly prohibited, or is it by default not allowed?
Edit: I ended up having a nice swim in Bear Wood Lake. One end of the lake had a sign Swimming strictly prohibited, dangerous water. The other end had a wooden platform with a ladder down into the lake. Very unclear but apart from if you can't swim you may drown I did not see any indication of danger and I don't know if the prohibition was just at the sign or at the entire lake.