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.

Post Office Seeks New Operator in Dinas Powys as Village Faces Loss of Its Last Branch
Gardening team praised after helping police clear fallen tree near St Brides Major
Specsavers calls on children in Barry to design Wales Deaf Rugby World Cup shirts
Whitmore High Named One of UK’s Best Workplaces for Development
Steel Signing Marks Major Milestone in St Richard Gwyn School Redevelopment
Two Rescues in Record Heat as Volunteer Teams Respond to Afternoon Emergencies
Police find evidence of a large-scale cannabis cultivation at Riverside Place property fire
Network Rail confirm closure of Brookside level crossing in Dinas Powys
Police given powers to ask people to leave Comeston Lakes Country Park
Planned children’s role play centre could be given the go-ahead by Vale Council
Marie Curie Garden Fayre deemed huge success
Council seeks views on Future of Colcot Sports Centre and Buttrills Playing Fields
First Minister quizzed on further devolution, budget decisions, and misinformation in FMQs
Extreme heat leads to changes to services and closures
Severe Heat Warning Set to Disrupt Rail Travel Across South Wales This Week
Communities asked to support older people across Wales during severe heat warning
Caribbean Community Wales Brings Wales‑Wide Launch to Barry This Weekend
Community Award winner calls for sanitary bins in men’s toilets after living with prostate‑cancer‑related incontinence
Cardiff Airport Backs Holiday Safety Campaign Honouring Rhoose Teenager Tom Channon