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".
More top news
The group planning a management buyout of Tata Steel's UK assets has confirmed its formal interest.
A pleasant afternoon with temperatures dropping under clear skies this evening.
A policeman impressed the skaters of Cardiff by borrowing a board and showing off his skills.