The RNLI is warning people that they are risking their lives by taking part in so-called 'tombstoning.'
A number of videos exist on the internet showing people jumping off cliffs around Wales.
Stuart Thompson, Divisional Lifeguard Manager with the RNLI, says that the changing nature of the sea means that conditions are unpredictable.
He warns that a jump that can be safely completed one day can become deadly the next.
This year has been a particularly busy year for the RNLI, who have not only had to deal with people getting into trouble on the water but also help those who were affected by the summer's floods.
The RNLI says a safer option for thrillseekers is to go on coasteering trips - a hobby that originated in Pembrokeshire.
TYF Adventure, based in St Davids, is one such coasteering company. In 2007, TYF and other coasteering companies worked with the RNLI and coastguards to establish minimum safety standards.
They say they want to discourage 'tombstoning' while working to benefit the local economy.
Some images courtesy of youtube