Advice from the ROSPA water safety code.
There are many dangers with water, which can include:
It can be very cold
There may be hidden currents
It can be difficult to get out (steep slippery banks)
It can be deep
There may be hidden rubbish, e.g. shopping trolleys, broken glass
There may be no lifeguards there
It is difficult to estimate depth
It may be polluted and may make you ill
