Murals designed to deter vandalism in a pedestrian tunnel have been covered in graffiti.
The design at Humber Bridge Country Park is called Ripple Effect and was unveiled in May.
Staff at the nearby Humber Rescue lifeboat charity, based in Hessle, East Yorkshire, found the damage on Sunday morning.
David Roberts, chairman of Humber Rescue, said: “I feel very disappointed and angry to think that someone would come down here and do such a thing in an area of natural beauty.”
Mr Roberts said he thought some parts of the murals had recently been given an anti-graffiti coating, but it would still be difficult to clean certain areas.
“I don’t think they realise what damage they’ve done. The mural is going to be here for quite a long time and, by the looks of it, so is their graffiti,” he said.
The murals were designed by local artist Emma Garness, in partnership with the Friends of Humber Bridge Country Park and Humber Rescue.
Les Nicol, who visits the park for a walk every morning, said: “It’s really sad. In fact, it’s worse than sad. It’s disgusting.”
East Riding of Yorkshire Council said: “It is saddening to receive reports of graffiti to the tunnel, which will be removed as soon as possible.
“Anyone with information on who may be responsible should contact the council’s anti-social behaviour team.”