Firefighters were called to a houseboat which had flooded and begun to sink on the River Thames near Nine Elms Pier in Battersea.
A 22m permanently moored houseboat was taking on water and had flooded to a depth of 1.5 metres. Three occupants got safely off the vessel and there were no reports of any injuries.
Crews worked to pump water from the boat until the tide went out.
Station Commander Mark Nunan, who was at the scene, said: "There were three people on board and they had woken to find their boat flooded and continuing to take on further water as the tide came in.
"When crews got there, the boat was flooded to a depth of around 1.5 metres.
"Firefighters from land stations worked with one of our fire boat crews to pump water from the vessel to stop it from sinking, but more water was coming into the boat as the tide came in.
"As the tide then turned and started to go out, crews were able to get the water level down to around 10cm and the boat came to rest on the riverbed. The occupants will now source further pumps until the boat can be fixed.
"We were glad to be able to help the occupants and often work with the houseboat community, giving water and fire safety advice."
Firefighters also liaised with the Port of London Authority to keep them up to date with the situation.
The Brigade was called at 0524 and the incident was over for firefighters by 1053. Three fire engines from Lambeth and Clapham fire stations, two fire rescue units from Bethnal Green and Lewisham fire stations and one of the fire boats from Lambeth River Fire Station were in attendance.