"The shell is 40 cm long with 10 cm diameter, and weighs 10 kg," said a defence official.
Authorities at the Jawaharlal Nehru Port Trust immediately alerted the Indian Navy after stumbling upon the shell last night.
"A team of explosives experts of Navy was immediately dispatched to the ship for removal of the shell from its dredging arm," the official said.
The shell had been sent for further analysis and safe disposal, he added.