Fifteen people accidentally lost their lives in the River Thames last year, according to the Royal National Lifeboat Institution (RNLI).
The charity lifeboat organisation saved the lives of 16 people in the River Thames during 2013 and rescued 344.
Over the past four years 34 people have accidentally died in the River Thames, with men accounting for 82% of fatalities during that time.
Slips and falls by the side of the river accounted for 21% of deaths.
By comparison, swimming and general leisure activities on the water accounted for 18% of fatalities over the four years.
In the last year, alcohol was a factor in three deaths on the river.
Cold shock risk
The RNLI said there was specific criteria as to what is classed as a life saved as opposed to just being rescued, as they have to be sure that if they did not save them, then there was no-one else who could have rescued them.
It added that a significant danger for people entering the water was cold shock, where a person gasps uncontrollably, drawing water into the lungs and causing a risk of drowning.
Despite warm air temperatures, the River Thames can cause cold water shock all year round.
Its average temperature is 12C (54F) but water shock can occur at any temperature below 15C (59F).
The charity operates at sea but also has four lifeboat stations on the tidal Thames at Gravesend, Tower, Chiswick and Teddington.
It has launched its Respect the Water campaign to highlight the risk of drowning in the tidal parts of the Thames and around the UK's coasts.
Guy Addington, the RNLI's coastal safety manager in the south east, said: "We want people to enjoy the river but we want them to understand there are risks, and that they should not underestimate the power of the water."