More than 30 north London teenagers who became trapped by rising coastal tides were rescued after using their mobile phones as distress beacons.
The 34 youngsters and two adults from the Ahvas Yisroel Community Centre were on a half term trip to the Kent coast.
They got lost in an area prone to rock falls and called Kent Police for help.
Mark Finnis, coxswain of Dover RNLI, said the group had passed "nine warning signs" deterring them from the walk.
"It could have ended up a whole lot worse," Mr Finnis told BBC London.
"None of the people we took on board our lifeboat were dressed in any attire that you would associate with clambering over rocks."
The Maritime and Coastguard Agency said the group were advised to use the lights from their phones to aid the search for them.
A rescue helicopter based in Lydd was involved in the operation, along with three lifeboats - two from Dover and one from Walmer - and the Langdon Coastguard Rescue Team.
"The group was located by one of the Walmer lifeboats in the area of active cliff falls and also spotted by a helicopter using the forward-looking infra red camera," said Richard Cockerill, UK Coastguard's senior maritime operations officer.
"All 36 people were recovered to safety by lifeboat and helicopter."
In a statement, the community centre in Stamford Hill, north London, said it was "hugely grateful" to the coastguard, whose "swift actions ensured that everyone was returned to the shore safe and well".
It promised a full investigation to "ascertain the facts".
It is understood the group had descended on to the beach from a coastal path between St Margaret's Bay and Dover when they were caught by rising waters, a coastguard spokeswoman said.
After being spotted using night-vision cameras, 31 members of the group were taken ashore and the remaining five were airlifted to the Dover Coastguard station.
All members were accounted for by 23:00 and were "safe and well".
"Thankfully, the quick and well co-ordinated search and rescue response meant all 36 were rescued and were lucky to escape without serious injuries, but they've had a traumatic experience," Mr Finnis said.
The Port of Dover later tweeted that the group's rescue "was a lesson to us all to be careful around water and check tidal information".