A community swimming pool run by volunteers is facing a bill of more than £1,000 after it was damaged by vandals.
The outdoor swimming pool in Heckington, which opened in 1974, was struck twice in the space of a week by intruders, who jumped through the protective cover into the water.
And police say it could be linked to other antisocial behaviour in the village.
Michael Wells, chairman of the swimming pool committee, said the pool had to be closed and children's parties cancelled.
"I was devastated," he said.
"It made me really upset and my immediate thought was 'just why have they done it?'
"Our volunteers have to fund everything and these mindless incidents are costing us a fortune."
Intruders first targeted the pool during the August bank holiday weekend, jumping into the pool fully clothed through the protective cover.
A similar incident occurred the following weekend, with the pool cover again being damaged.
"We had to cancel two parties which means we have lost about £100 just from that," said Mr Wells.
"Then there is the new pool cover, which we expect to cost about £800 and any losses from general admission.
"Added to that, with the time and materials we have had to use to cleanse the water, it is going to cost about £1,000."
The pool remains closed while work is carried out to clean the water and make it safe for use.
Lincolnshire Police are investigating the incidents.
Aimee Burge, spokesperson for Lincolnshire Police, said: "The initial incident was a report of burglary and criminal damage, which occurred some time between the evening of Sunday, August 26 and the afternoon of Monday, August 27.
"Offenders climbed over the fence to the swimming pool and then broke into the shed, stealing a number of food and drink items.
"The offenders also swam in the pool, causing damage to the pool cover.
"The second incident was of criminal damage and occurred some time between the evening of Saturday, September 1 and the morning of Sunday, September 2.
"Again, the offenders swam in the pool and damaged the pool cover.
"The investigation is ongoing and police are linking it to a number of recent antisocial incidents in the area."
Anyone who has any information is asked to call the police on 101, quoting incident 275 of August 27 or 180 of September 2.
Alternatively, call Crimestoppers, anonymously, on 0800 555111.