The Isle of Man Constabulary is appealing for witnesses after a red Lexus UX had its rear window smashed in Fenella car park, Peel last week.
The incident occurred on Wednesday, July 9, at around 9.20pm.
Police say a rock, about the size of a tennis ball, was thrown or kicked from the cliffs above, striking the vehicle parked on the seaward side.
Officers have ruled out falling debris or accidental dislodging due to the distance from the cliff.
Officers say the rock could have caused serious injury if it had hit a person.
Anyone with information is asked to contact Police Headquarters on 631212, quoting reference number 97/5148/25, or anonymously via Crimestoppers on 0800 555 111.