The RNLI is warning young people who participate in 'tombstoning' that they are taking their lives into their hands.
They say it's only a matter of time before someone is killed or seriously injured jumping off Wales' cliffs.
Some images courtesy of youtube
Stuart Thompson, from the RNLI, says one of the risks of tombstoning is the sheer unpredictability of the environment.
"The problem is that you know heights of tides change, conditions change" he says.
"The conditions of the seabed change as well so it's actually quite a dangerous practice".