The wreckage of a car was among several items of junk elevated from the seabed off Valletta during a clean-up on Saturday morning.
It is not yet known how the car ended up in the sea though it could have been the result of last February's vicious storm, which caused record damage.
The police are investigating.
According to the clean-up organiser Mark Camilleri, several car tyres, poles and heavy engines were collected from the seabed.
In total, almost 20 kg of non-recyclable plastic, 90kg of metal and 13kg of batteries were elevated, together with almost 500kg of bulky waste.
The event was mainly organised by the QLZH foundation, an offshoot of Quicklets and Zanzi Homes with the help of Dive Systems, Żibel Malta and Wave of Change.