Extinction Rebellion has floated a submerged house down the Thames to send an "SOS" to the government about the threat of climate change and rising sea levels.
The stunt coincided with severe flooding destroying houses across parts of Derbyshire and Yorkshire – something that XR said was a stark reminder of the "very real risk".
The Intergovernmental Panel on Climate Change has warned of a rise in sea level of two metres by 2100, while climate scientists predict it may rise between one and five metres.
Under new sea level projections, Stratford, Barking, Dagenham and parts of south and east London, East Anglia, Essex and Kent could be under water by 2050.
Stephen Harrison, head of the UK Climate Expert Committee, believes the IPCC is underestimating the threat.
"We may be close to passing a tipping point for at least some of the large outlet glaciers draining the West Antarctic Ice Sheet and this would commit us to significant sea-level rise whatever we decide in terms of reducing greenhouse gas emissions," Harrison said.
The "sinking house" was built by Katey Burak and Rob Higgs.
In a statement, the pair said: "We want to respectfully raise awareness of the severity of the impending human-made disaster. We need urgent action to address the climate emergency and devastation of our beautiful and precious natural world, which is being decimated at an unprecedented and tragic rate."