Emergency crews have rescued four children after they got stranded in the water "up to their necks”.
The youngsters were seen waving for help when they got into trouble while making their way home from Mulberry Harbour near Thorpe Bay, in Southend, on Friday.
HM Coastguard Southend confirmed they had helped save the children using a hovercraft at around 3.15pm.
Their mum had called 999 for help from the shore, they said in a statement.
“(The children) attempted to make their way back to shore but the water was too deep and caught them unawares and at one point were observed up to their necks in water and waving for help,” the coastguard said in a statement.
They warned people not to walk to structures when the tide was low, adding: “Do not walk out to any man-made hazards or structures at low tide you may see in the 'near or far' distance off Southend, you will put your and your families lives at risk!
“Check the weather forecast, tide times and read local hazard signage before setting out for the coast whether on the beach, mudflats or on the water.
“Coldwater can be silent and deadly. Even on the warmest of days. It kills!”
The children were diagnosed with onset hypothermia and taken to hospital to be treated.
They later returned home where they are recovering.
The coastguard said: "We wish the four casualties a quick recovery, who we understand are now back home."