A 50lb case of gelignite was retrieved from Carrick Harbour by a diver in May 1968 after it fell into the water whilst being unloaded from a boat.
It was the second time that gelignite had fallen into the harbour.
The case fell from the Glaswegian vessel ‘Reylight’ which had been missing a safety net.
The spot where the case fell into the sea was marked. A police officer was on guard until the case resurfaced.
A diver was brought from Belfast to retrieve the explosive.
It had been part of a 50-ton cargo which had been transported from Greenock destined for quarries across Northern Ireland.
Captain David Ford said: “It was not dangerous at all but we had to bring in a diver.”