An investigation has been launched into jet ski activity in the Truro and Penryn Harbour area as complaints over anti-social behaviour involving the equipment rises across Cornwall.

Issues have also reported at Porthpean, St Ives and Padstow, while in Penzance hundreds of residents have signed a petition asking for them to be banned.

Devon and Cornwall Police have said they have noted a rise in complaints after a potential conflict between beachgoers and jet ski users at Mounts Bay, as well as with swimmers off the Battery Rocks to the south of the harbour.

Cornwall’s maritime manager Christopher Jones said: “This is an increasing trend. Sadly, alongside all those jet ski users who are considerate and respectful of other sea and beach users, there is a small element who behave antisocially, even dangerously.

“In Cornwall, harbour masters, police and coastguards are concerned about the potential conflict between these fast and sometimes unstable vehicles, and others using the water to make their living or for leisure.

"All the maritime agencies are working together to improve safety for coast, harbour and beach, and we will be keeping a close eye on jet ski and powerboat use this season.”

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Loic Rich, Cornwall’s Harbour Board chairman, said: “We recognise jet skiing is a legitimate and popular sport, but we must challenge irresponsible and antisocial use where personal safety and navigation of other vessels is put at risk.

“Beachgoers and swimmers, including so-called ‘wild swimmers’ at sea, have felt threatened by the speed and proximity of personal watercraft.

"Our Harbour Authority staff across Cornwall Council’s 12 harbours will be working closely with the police and HM Coastguard, and making use of CCTV to identify offenders. This can result in prosecution, and seizure of the jet skis concerned.”

Guidance on safe use is published by the Personal Watercraft Partnership, and advises against ‘wave jumping’ behind boats, revving engines in shallow beach areas, weaving in and out of anchorages, and entering areas where there are swimmers.

New measures have now been agreed with the Penzance harbour master, including new signs for the slipway, agreement forms for all users, the handing out of safe use of slipway/harbour guides, and increased manning of the slipway. The charge for jet skis to use the slipway is £10 per launch, £40 per week or £150 annually.

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Loic Rich added: “Unfortunately jet skis fall outside of much maritime legislation which hampers responding with meaningful powers. But we are reviewing this and hope as a local authority we can gain more control over jet skiing.

"We ask the public to be vigilant and to please report any dangerous occurrences involving jet skis, or other small craft, to the relevant harbour office or to police.”  

Jet skis don’t have turning propellers or outboard motors, but like powerboats their jet propulsion makes them able to skim across the water surface at speed.

Cornwall Council has advised they are best suited to calm water conditions, and where they are prohibited is mostly governed by local authority bylaws.

In Cornwall’s Carrick Roads in the Falmouth and St Mawes area there are parts of the harbour area where they aren’t permitted, and there are restrictions on their speed near beaches and in some working harbours where they may be a nuisance to other harbour users.

No licence is needed to jet ski in UK waters, unless taking part in organised racing. They are more tightly regulated in other countries – for example jet skiing without a license in Portugal carries a fine of up to £2,650.

As for all types of boat, insurance is recommended, but not legally required– including public liability insurance in case of injury or damage to property.