Four large solar panels have been stolen from target barges, moored off the shore between Pembroke Dock and Neyland.
The solar panels, valued at £1,142, are made by Solara and are 59cm by 46cm in size and in the shape of the roof of a house.
They are black in colour and made from stainless steel and plastic. Electrical diodes were also stolen from the barges.
The crimes occurred on two separate occasions. The first between August 3 and 8 and the second between October 3 and 10.
The offender would have had to have used a boat to carry out the crime.
Any information, please, to Pembroke Dock police station or DC White at the Marine Unit on 0845 330 2000.