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
Andrew Lauder, from Wenvoe, south Wales, has been branded a "serial groper".
The deal is welcome news for the site in Broughton which manufactures wings for the aircraft.
Fans queued for hours to get a glimpse of the Royal Couple as they tour Cardiff Castle and visit a community centre.