A large catamaran has sunk on the River Foyle overnight.
The MMV Ostrea- believed to be about 50ft in length- was all but submerged by first light this morning.
It is understood the large boat is used by the Loughs Agency for dredging the Foyle riverbed.
The boat is believed to have been docked all night at Foyle Marina and the cause of the sinkage remains a mystery this morning.
Supporting seacraft and Northern Ireland Fire & Rescue service personnel were witnessed at the scene this morning at Foyle Marina, and appeared to be using ropes to try and stop the craft sinking further.
A number of leisure boats and other craft were docked on the near side of the marina this morning and it remains unclear whether these will have to be moved.
Only one of the hulls of the catamaran remained above water.