Six children and three adults have been pulled to safety after getting trapped by the tide at Treyarnon beach in north Cornwall.
They were left clinging to rocks as water flooded in on Tuesday lunchtime.
The youngest was seven.
Lifeguards from Constantine rescued the group.
RNLI lifeguard Andy Houlder paddled round the rocks on a rescue board while Senior RNLI lifeguard Martin White responded on foot. From both vantage points, the lifeguards could see that a total of nine people, including six children aged between 7 and 12 were trapped.
They were huddled together on a rocky platform above the gully which was quickly filling with water as the tide came in, and with a solid five foot swell washing though, they were in danger of being swept off the rocks.
The gulley has a deep cave at the back so the only way out was the way the group had come in, but with the incoming tide and increasing surf, it was too dangerous to attempt.
Martin called for backup from RNLI lifeguards Zahli Lowe and Dan Lee who responded in the inshore rescue boat (IRB) from Constantine.
Martin said: "Because of the shape of the gully and the size of the swell it was impossible to get the IRB or even the rescue board in close enough to pick up the casualties so the only way was to swim in.
"Myself and Andy swam in with rescue tubes, and communicated with Zahli and Dan who were standing off in the IRB. They could see when a set of waves was coming though so we could time our exit in the lull between sets. We swam two children out first, with a dad who was helping another child, we dropped them off at the beach 15 metres away and returned for the second group.
"We repeated the process with the other three children and one of the adults who was a stronger swimmer helping one of the children.
"Andy returned to help the final adult, dropping them off at the IRB.
"It was a very difficult and long process, made even worse by the time pressures of the incoming tide and a building swell. Thankfully we all know this beach and stretch of coastline very well and were able to read the waves and get them all out safely."