Around £1,000-worth of damage has been caused to a boat moored off the coast of Haverigg.
The damage to window was caused between May 25 and June 15 and police said they were keen to hear from anyone who has information, particularly any dog walkers or anyone else who may have passed at the time and saw anything suspicious.
The boat was moored near the Harbour Lights caravan park.
Anyone with information can report online at www.cumbria.police.uk/report-it, quoting incident 33 of June 15, for the attention of PC 2642 Rebecca Clark or call on 101.
Alternatively, contact Crimestoppers anonymously on 0800 555 111.
