Police are warning would-be tombstoners against the dangers of jumping from Penarth Pier.
It follows isolated reports of people jumping into the water from the Victorian pier.
Officers have been carrying out high-visibility patrols around Penarth and other coastal areas of the Vale as part of their annual Operation Elstree crackdown on anti-social behaviour.
South Wales Police say they'll continue with regular patrols over the rest of the summer in an effort to deter tombstoning.
A police spokesperson said: "While they can look tempting, many bodies of water have unseen hazards below the surface, or strong currents. Cold-water shock can also mean that even strong swimmers can get into significant difficulty."
"People need to remind themselves of the risks and act responsibly, while parents are also urged to remind their children about the dangers."
"Cold water shock, unpredictable currents, and unknown hazards beneath the water’s surface all pose a serious risk."
" Anyone who enters the water from the pier are risking their lives, and potentially the lives of others, should they need to be rescued."
Vale of Glamorgan Council said it was aware of people jumping off the pier into the sea - with the incidents being reported to police.
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