Youngsters are risking their lives jumping into the sea off a causeway in Weston-super-Mare.
The town's coastguard team raced to the seafront yesterday evening (Wednesday, July 17) after a member of the public reported a group of youths jumping off the sea wall at Knightstone Island.
However by the time crews arrived, the teens had disappeared.
Tombstoning is the act of jumping in a straight vertical posture into the sea or other body of water from a high jumping platform, such as a cliff or harbour edge.
This posture of the body, resembling a tombstone, gives the activity its name.
Large numbers of people have been seriously injured across the UK from taking part in the activity.
Coastguards are warning of the dangers and say often the water, although it looks deep, may harbour hidden dangers.
A spokesman for Weston Coastguard said: "We received reports of a group of youngsters jumping into the sea from the Knightstone harbour wall.
”Tombstoning is an extremely dangerous and potentially fatal activity to partake in.
“Since 2004 the coastguard has dealt with over 200 incidents, with 70 injuries and 20 deaths around the UK.
“Although the water may look deep, there are often hidden dangers, which can easily catch people out.
“The strong currents and tides around Knightstone Harbour can easily result in people not being able to swim back to the slipway, being swept into deeper waters.
“Now the summer holidays have begun, we want young people to enjoy themselves if they come to the beach, but we urge them to not put themselves or their friends at risk."
In the past Knighstone Island has been a popular location for young people tombstoning in the hot weather.
People also tombstone at quarries and in the past off Weston's Grand and Birnbeck piers.
Three years ago a tourist was left with back and spine injuries after jumping off the Grand Pier on Weston beach.
Anyone that sees anyone in trouble along the coast should call 999 and ask for the coastguard.
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