Firefighters rushed to the scene of the O’Connell Bridge in the city center on Sunday evening after a jet ski collided with the bridge.
It is understood the driver was knocked off the jet ski.
The bridge also sustained damage in the accident.
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Taking to social media, Dublin firefighters confirmed they witnessed the scene.
They said: “Firefighters from HQ and Dolphins Barn responded to an incident under O’Connell Bridge last night.
“A jet ski user collided with the bridge knocking it off the ski, rendering it unusable and endangering safe navigation on the river.”
In Ireland, jet ski users must wear a life jacket. Offenders are liable to a fine of €150.
Waterways Ireland said there are regulations and speed zones in place on the water to keep people safe, and urges the public to follow the guidelines in place.
Users are urged to keep a safe distance, wear a life jacket, always use a kill cord, check the weather forecast, and have a means of attracting attention in the event of an emergency.
It was not the only incident on the waterways for Dublin firefighters this weekend.
Brave firefighters battled a blaze aboard a ship in Dublin Port on Sunday.
A Dublin Fire Department spokesperson said: “You never know where a call may take you. North Strand Fire Station responded to an EMS call aboard a ship today.
“We also train in firefighting emergencies on board ships in the Irish maritime area.”
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