The RNLI lifeboat crew in London said “heroic” Scot Natalie Harrison carried out “a risky, but utterly selfless and incredible act of public service”.
The drama unfolded on Monday when London Coastguard requested the launch of a lifeboat crew after reports of a woman in the river by Bankside Pier, near Shakespeare’s Globe theatre.
The crew rushed to the scene where they found a member of the public gripping the hand of a woman in the water.
Ms Harrison, the Scottish rescuer, was keeping the casualty afloat, stopping her from drifting away in the dangerous tidal flow of the Thames.
Steve King, full-time lifeboat helmsman at Tower RNLI lifeboat station, said if it had not been for her actions, the woman in the river may not have survived.
As they made their way to the scene, Mr King said the crew saw a blonde-haired figure hanging over the safety barrier and holding on to the woman in the water.
“We got in close and one of the staff from the Thames RIB Experience boarded the lifeboat to help us pull the woman from the river.
“If it wasn’t for Natalie’s heroic efforts she may have already gone under and we might not have been able to save her,” he said.
The woman in the water, thought to be in her late 20s or early 30s, was conscious and was breathing when she was pulled onto the lifeboat, but was wet, cold and distressed.
Mr King said: “As a general rule, the RNLI doesn’t encourage what Natalie did - if people enter the river or sea to try to rescue others they risk getting into difficulty themselves, which exacerbates the rescue situation for emergency services.
“We normally advise people to raise the alarm and call the Coastguard.
“That said, there’s no denying what she did was utterly selfless, an incredible act of public service.
“I believe she was on holiday in London and was nearby when she saw the woman in the water, and acted immediately to help.
“The woman in the river was vulnerable and me and my fellow lifeboat crew members feel Natalie’s brave actions may well have saved that woman’s life.”
The RNLI is currently in the midst of its annual Respect the Water campaign, a safety initiative aimed at reducing the number of accidental drownings around the coastline and in inland waters.