Four people had to be rescued from the River Thames at Waterloo Bridge on Saturday after their rowing boat capsized.
The London Fire Brigade (LFB) attended the scene, and all four people were rescued safely.
But LFB highlighted that none of the passengers were wearing life jackets.
In a statement on the London Fire Brigade's website Watch Manager Craig Weeden said: "They had simply taken on too much water and capsized. We pulled them from the river and towed their rowing boat back to the RNLI pontoon and got them ashore.
"Luckily there were no injuries today and no-one required any medical assistance but none of the four people we plucked from the water was wearing a life jacket.
"When we got there the only thing keeping the two men and two women who had been aboard afloat was their upturned boat. If you are out on the river in a small boat it is essential you wear a life jacket."
The Brigade's fire boat, Fire Dart, is based at Lambeth River Station, and was called at 15.27. The incident was over by 15.33.
Back in June 2013, a father-of-two died when his kayak capsized in the River Thames as he attempted to navigate a dangerous weir.
And, just last week, a man drowned trying to swim across the River Thames after missing the last ferry home.
The man, who was thought to be in his twenties, died on Thursday (1 August) evening at Hampton, Middlesex.
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