On just one day last week, three people entered the waters of the River Thames and did not resurface, one at Waterloo, one at Kingston-on-Thames and one at Shadwell Basin.

An extremely hot day can make the Basin seem an inviting refuge from the heat, but too many people fail to realise the dangers of swimming there.

Large bodies of water are always very cold. Even a heatwave does not make the water warm. The shock of jumping into cold water drains all the energy from the body.

The warning signs forbidding swimming in Shadwell Basin are there for a good reason. The water is dangerous at the best of times; hidden obstacles lie in wait beneath the surface.

Despite this, hundreds of young people come from all over London to use the Basin as an outdoor swimming pool.