COASTGUARDS are urging members of the public to report suspicious sightings immediately.
It comes after the Weymouth RNLI Inshore lifeboat searched for a possible partially sunken dinghy just off Portland Harbour on Wednesday.
The incident happened at around 4.15pm.
The rescue team found what turned out to be debris which matched the description.
A spokesman for Portland Coastguard said: “The member of the public who reported this sighting only did so after a three-hour delay. HM Coastguard stresses the importance of reporting any suspicious sightings as quickly as possible.
“Time is a critical factor in any marine or coastal search and rescue situation.”