On Thursday morning, Hong Kong residents called the emergency service and police and claimed that they had seen a sinking barge with cargo in Victoria Bay.
Everybody was aware of the news, but a little later it became clear that the barge was not sinking. It was specially submerged in order to unload concrete caisson.
This is how they usually work when transporting heavy loads. The caisson was then sunk to the bottom of the bay for further technical works.