There is nothing more suitable for swimming than places officially designated for this purpose.
In such places for swimming there is everything necessary, and in case of emergency you can count on the help of rescuers and doctors.
If a combination of circumstances has brought you to a wild beach, the first thing you should do before diving into the water is to make sure that it is clean.
Resist the temptation to dive near a sign that says swimming is prohibited. Such signs warn of possible dermatitis and allergic reactions (at the very least).
At the most, sewage and industrial waste may be discharged into bodies of water on the banks of which prohibiting signs have been installed.
In addition, it is not recommended to dive into stagnant water where there is mud.
Inspect the surface of the water - if there are snags sticking out of the pond, this place is also not suitable for diving.
And, of course, try to stay away from the ducks - such "neighborhood" will not lead to anything good.