New measures have come into force in Bridlington to deal with youths diving off rocks and cliffs into the sea.
Police said they had been called at least once a day to reports of groups of up to 30 youths or more jumping off rocks, the pier and walls.
They say the most common places for "tombstoning" are the Harbour Wall, the Floral area and the steps near the Spa.
A dispersal order around the harbour and seafront has been brought in to enable police to move youths on.
Under the terms of the order, police have the power to tell people in groups of two or more to disperse and not to return for up to 24 hours.
To remain or return to the area having been told to leave is an offence and can lead to being arrested.
The order has been brought in by Humberside Police and East Riding of Yorkshire Council following complaints about young people in the area.
Police Community Support Officer Andrea Humphrey said: "Officers are called at least once a day to the seafront to deal with youths jumping and diving off the pier and walls.
"I have stopped people from as young as 10 years old and even some adults jumping off the pier, who do not see the danger of the dire consequences should they slip or jump in the wrong place."