US businessman Gregg Bemis, owner of the Lusitania which was torpedoed off Co Cork with the loss of 1,200 lives during the first World War, has died in New Mexico.
Mr Bemis was due to mark his 92nd birthday next week.
Deep-sea diver Eoin McGarry, who was a close friend, said he had never seen anything like his persistence and tenacity.
“He always wanted to find out what caused the second explosion on the Lusitania, and the mantle we have to take on is to find that out,” Mr McGarry said.
In 2016, Mr McGarry retrieved one of the telegraph machines from the ship under license from the Department of Heritage.
Bemis, who dove on the wreck at the of 76, acquired joint ownership of the Lusitania in the 1960s. He then bought it outright for one US dollar.
He fought a long legal battle to verify his ownership, involving court hearings in three countries including Ireland.
The former venture capitalist was determined to find the cause of a second internal explosion on the ship which occurred after the German torpedo of May 7th, 1915, and which is believed to have accelerated its sinking in just 18 minutes with devastating loss of life.
There were at least 90 Irish men, women and children among 1,197 passengers and crew who died. Among them were art collector Sir Hugh Lane, James McDermott, the ship’s surgeon, and his assistant, Dr Joseph Garry, and the composer Thomas O’Brien Butler.
Also on board was one of the richest men in North America at the time, Alfred Vanderbilt.
An underwater heritage order was placed on the Lusitania wreck in 1995 by the then arts minister, Michael D Higgins, as he considered it a grave which required both protection and “regulated” and “transparent” investigation.
Bemis supported several expeditions – including a National Geographic dive in which he descended to view the wreck from a submersible.
However, six years ago he said that onerous licensing conditions were frustrating attempts to establish the cause of the second explosion. The Department of Culture denied the claim.
He also said he believed Ireland was not deriving benefits the tourism value of the Lusitania as a long term source of revenue, both in funding a museum for its artifacts and encouraging visiting divers.
During a diving expedition in 2008, Mr McGarry found four million rounds of ammunition on board. They were classified as small arms ammunition which was permitted to be carried on board.
Mr McGarry believes the cause of the second explosion may never be resolved.
Last year, Mr Bemis signed over ownership of the wreck to the Old Head of Kinsale Lusitania Museum at a ceremony at the Old Head of Kinsale which is the nearest point of land to where the ship went down on May 7th, 1915.
“I’ve come to realise that, at almost 91 years old there is only so much more I can do to further this project and I think because of the Lusitania’s part in history, it’s very important that it be done properly and we get all the artifacts we can from the wreck to put in the museum planned for here,” he said.
Mr Bemis explained the deed of gift would not become effective immediately, given that it might impact on the local museum committee’s ability to raise Government and State funds He said it would be held in escrow and activated at short notice in the event of his death or when the museum is built.
Con Hayes of the Old Head of Kinsale Museum Committee said Bemis was a remarkable man and his generous gesture to transfer ownership of the wreck would "not be forgotten".
“Gregg has been ill for a number of years but he was quite determined to come to Ireland last year to formally hand over the ownership of wreck to us and that’s something for which we will be eternally grateful,” said Mr Hayes, recalling how he had first made contact with him in 2011.
It was the sinking of the Lusitania that influenced the US government's decision to declare war on Germany in 1917.
New imagery of how the ship looks on the seafloor is reproduced in a recently published book - RMS Lusitania- the story of a wreck, by Fionnbarr Moore, Connie Kelleher and Karl Brady of the National Monuments Service, Charise McKeon of the Geological Survey of Ireland and Ian Lawler of Bord Iascaigh Mhara.