Jet ski users are being urged to practice safe fun in the sun, following a spike in complaints in the Canterbury region.

The complaints are a concerning trend with Environment Canterbury dealing with more complaints than usual at this time of year, with members of the public reporting sightings of jet skiers riding too close to the shore.

ECan's navigational safety officer Gary Manch said people can still have fun while minimising the risks and all jet skiers should make a point to know the rules, so they can play it safe in the sea.

Mr Manch said he's worried about what he's heard, with at least one complaint every couple of days.

Most of the complaints were centred in Sumner and Lyttelton, but there's also been one incident in the Ashley River estuary.