Beachgoers have been warned of "dangerous" incoming tides which "move quickly" after eight people were cut off and had to be rescued.
The coastguard was called at 12:30 BST on Saturday to help the group trapped by a locked gate at the bottom of the 39 Steps near Joss Bay in Kent.
The rescue team was able to gain access to a path and helped the stranded people to safety.
HM Coastguard duty controller Duncan Ley said they were "extremely lucky".
Beaches around the coast have been packed with people enjoying the sun and cooling off as a heatwave grips the UK.
Mr Ley said said there could have been a "very different outcome" at Joss Bay.
He said: "The UK's coastline is spectacular to explore - especially on glorious days like today, but incoming tides move very quickly and they can also be very, very dangerous."
He advised coastal walkers to check tide times and the weather forecast before setting off.
He added: "Carry a fully-charged mobile phone and tell someone where you are going and what time you will be home.
"If you do get cut off by the tide, don't attempt to climb cliffs as a short cut back to the top and do not attempt to self-rescue yourself or someone else if they get into difficulty.
"Our coastguards are skilfully trained in all manner of rescues, in all terrains and waters."
He said anyone in difficulty should call 999 and ask for the coastguard.