For people who are interested, there are a lot of places that offer wild swimming with a lifeguard and often other faculties:
https://nowca.org/nowca-lake-directory/
And there are many many places around the country that offer introduction to wild swimming courses where people can try out wild swimming with an instructor for example this one:
https://www.diverscove.co.uk/intro-to-open-water-swimming
In addition the outdoor swimming society have a Facebook page where if you join you can ask about safe swim spots local to wherever you live.
pretty much wherever you are in the country there are groups of wild swimmers and they will often know where is not so safe to swim and where is better. There’s also often local Facebook groups for your area which you can find from the outdoor swimming society.
so you can check out where they are going and see what the dangers are likely to be.
https://www.outdoorswimmingsociety.com/
in general drownings are often in situations where people do not know the river or lake they are swimming in and there are strong currents plus ystt usually a bit of teenagers egging each other on.
a rash vest might help with sunburn but it won’t do anything about teenager peer pressure or strong currents,
The safety advice for if you get into trouble in any water - sea, lake, river or reservoir, is float to live,
float on your back, your natural buoyancy will keep you pretty high up.
https://rnli.org/safety/float