When wild swimming in the UK, you'll see plenty of signs warning of deep water, forbidding paddling or swimming, and, carrying a variety of other intimidating messages (many of them a consequence of the Draconian 1984 Occupiers, Liability Act). But where does the law stand on this issue?
Things are restricted in England and Wales (unlike Scotland where they have right of access secured by the Scottish Land Reform Act of 2003). From Waterlog by Roger Deakin, 'only where a river is navigable do you have rights of access along its bank' (p33, Deakin 1999), and tidal waters (with exceptions - check local bye laws). This right extends to places where there exists a historical precedent, custom, longstanding tradition or established use. Swimming in reservoirs is a 'no no'! (Take this last one from someone who was caught by the fish-Fuzz doing just that).
Access to the water is a trickier thing altogether. When determining access think public rights of way, bridges and footpaths, lake shores and fjords. If confronted, be aware that for a start, trespassers CANNOT be prosecuted (trespass is covered by civil law of Tort and not criminal law, and you can only be prosecuted under criminal law). If you are courteous and have not led the landowner to incur damage by your actions then there is little the landowner can do, short of requesting you leave the water. You are within your rights to request proof of identity or authority. If you are on a public footpath then you cannot be asked to move on.
You can find more details here and here. There are plenty of grey areas, but be discreet and you should be ok!
The other big scare tactic is Weils Disease. This is a bacteria (Leptospira) carried in the urine of rats, cattle or dogs which enters the human body through lesions in the skin or 'mucous surfaces' (nose, mouth or conjunctiva)
To Roger Deakin's Waterlog once more, in which he quotes epidemiological research from the University of Bristol,
- "There are on average each year in the UK, some 2.5 cases of Weil's disease associated with bathing and water sports (ie one case among every two million annual recreational water users). As the case fatality rate in the UK is 10-15%, the chance of dying from Weil's disease associated with bathing and water sports is about 1:20 million expose persons"