Three men have died after being pulled from the sea at Camber Sands on the hottest day of the year.
They were all recovered from the water by emergency rescue teams at the East Sussex beach within 30 minutes of each other.
Seven other people have died around the coastline since Friday, all of which were linked to stormy conditions.
The public is being asked to stay away while emergency services deal with the incident.
Coastguard helicopters, a lifeboat, rescue teams and an air ambulance were sent to the scene after reports the three were in need of urgent medical assistance.
Sussex Police said it was not yet known who the men were or if they knew one another.
Emergency teams were called at 14:10 BST to reports of a person in difficulty in the sea. On arrival a second and third person were found to need assistance within 20 minutes of the initial call-out.
Eyewitness Natalja Taylor, 30, said she saw three people being pulled out of the water, apparently by “regular people, not emergency personnel”.
“There were so many people there. They were still on the beach when we left,” she said.
She said police drove on to the beach with a loudspeaker telling people not to go into the water until further notice, and also taped off “a huge chunk of the beach so no-one could get near it”.
She said: “It’s pretty scary. I’m not sure how it happened. We decided not to go into the sea after seeing warning signs about some kind of fish.
“It wasn’t particularly windy down there, it was just a hot, sunny beach day.”
It is understood the incident did not involve jellyfish.
Charlotte Frederick, from London, who saw the rescue operation take place, said: “One was taken away on a rescue truck and the other two were left behind.”
She said she realised later that the other two men had also died.
“We saw them take up a blanket and then after that we saw them taken in a body bag. It was really distressing,” she said.
The incident happened on the hottest day of the year when the beach was packed with people.
Ch Supt Roskilly said: “This has been an incredibly tragic situation and very traumatic for those who were there on the beach at the time.”
‘Extremely rare’ incident
Last month, 19-year-old Brazilian Gustavo Silva Da Cruz died after getting into difficulty while swimming in the sea there. He was one of three men who got into trouble in the water.
Camber Sands is a popular destination for beach-goers and Rother District Council provides beach patrols there throughout the summer.
A council spokesman said: “While it’s very upsetting to see two similar, tragic incidents this summer, over the years these kind of incidents are extremely rare and on a fine day around 25,000 people use the beach safely.”
He said the beach patrols were able to advise people of potential dangers, reunite lost children with their families and deal with incidents on the beach.
“Although it’s too early to draw any conclusions from this latest incident, in recent years we have seen a change in the make-up of visitors to Camber, including more people from outside the area who are not familiar with the sea and the dangers it can pose,” he said.
He said incidents had included visitors entering the sea even though they could not swim, and in some cases going into the water fully-clothed.