UK heatwave: Warning to Milford Haven 'tombstoners'
Dozens of thrill seekers have been "tombstoning" into water in a coastal town every day during the heatwave, according to a report.
A port authority said up to 60 people per day had been jumping into water from height in Milford Haven.
The Port of Milford Haven said it would enforce its bylaws, as it had previously, to ban the activity.
It said that risks include potential "death traps" under the water such as shopping trolleys and tyres.
The port said it was "simply trying to prevent a serious injury or at worst a fatality".
It added: "If we find anyone jumping into the water, we will be exercising our right, as land owner, to prosecute."
There have also been reports of people jumping in despite boats being in the area, with one near-miss incident.
As well as the risk of what swimmers might hit when they jump in, the RNLI said it was also concerned about cold water shock, where a swimmer's risk of inhaling water increases.
It added that anyone considering jumping into the sea from height should check for hazards like submerged rocks and consider the depth of the water.
A jump of 10 metres (16.4 ft) requires a depth of a least 5 metres (32.8 ft), it said.