The historic SAS Durban warship at the city's maritime museum has partially sunk in the harbour.
In a statement on Tuesday, the acting harbour master at the port of Durban, Capt Justin Adams, said the ship took on water overnight.
“The vessel is understood to have taken on water overnight and sunk partially in shallow water with no individuals on board,” he said.
There were no concerns of pollution as the vessel had no oil on board, he added.
The warship was built in the early 1950s to counter the threat posed by naval mines. According to the Durban local history museums website, the SAS Durban was one of three known survivors of the Ton-class minesweeper first developed for the Royal Navy in 1955.
It was handed over to the museum in 1988 and used as a floating exhibit. It was recently reopened after undergoing renovations.
The eThekwini municipality has deployed diving teams to investigate the cause of the sinking, said Adams.