An RNLI lifeboat crew carried out two rescues on Friday of people trapped on the Thames foreshore.
The charity's lifeboat happened to be on a training exercise with police and fire service boats when the RNLI crew spotted the young girl and two adults waving frantically from the shoreline at Millbank, several metres below the river wall.
They had been exploring the exposed river bed when the tide turned and rapidly rose around them, cutting them off from any means of escape, at around 11.50am on Friday.
Craig Burn, Tower RNLI lifeboat helmsman in command, said: "We could see the young girl and who we think were her parents waving frantically from shoreline. It was clear they were in a dangerous situation. They were pinned against the river wall by the tide which had almost reached their waists.
"It would have only been a matter of minutes before they were swept away by the fast flowing flood tide. People often don't realise that the River Thames can flows faster than an Olympic swimmer can swim, so it can all too easy knock you off your feet and sweep you away."
The RNLI crew brought the young girl and two adults aboard and took to them to the safety of Millbank Pier. As they were disembarking the lifeboat crew received an emergency radio call from London Coastguard to a report of a man stuck in the mud close to Potters Fields Park and Tower Bridge.
Craig added: "We quickly arrived at Tower Bridge and spotted a man in his twenties clinging to a chain at the river's edge with the water around his ankles. He had been taking photos of Tower Bridge when he got cut off by the rising tide.
"I'm not sure how long he could have held on for but he could have easily been swept away by the fast flowing current as the water rose around him.
"We got the guy aboard and took him to St Katharine's Pier. We're having exceptionally low tides at the moment which seems to be encouraging people to climb down to the exposed foreshore.
"If you are going to do this, please check the tide times beforehand and always be sure you have a means of escape back up to the embankment above."