Lex Warner, 50, died in 2012 after getting into difficulty while diving off the M.V Jean Elaine operated by Orkney-based Scapa Flow Charters.
The Court of Session previously rejected a legal action from Mr Warner’s wife, Debbie, ruling it time-barred, but later allowed one from his six-year-old son, Vincent.
Next month Scapa Flow Charters will go to the Supreme Court in London to appeal the Scottish court’s decision.
Mr Warner, a building company director from Sutton Coldfield in the West Midlands, was part of a group diving on a ship wreck 15 miles off Cape Wrath, Sutherland in August 2012.
According to court documents, he fell on the deck of the boat while wearing his full diving gear shortly before going into the water.
After being helped back to his feet, he continued his dive and descended to a depth of 88 metres (290ft) before getting into difficulty and attempting to rise to the surface.
He stopped breathing and despite attempts to revive him onboard the ship, was pronounced dead a short time later.
Mr Warner had just heard from his wife that she was expecting their second child shortly before his death.
Six weeks after his death, Mrs Warner suffered a miscarriage.
A ruling from the Court of Session in 2016 found Mrs Warner was unable to sue for damages because too much time had passed since her husband’s death.
But last year it was ruled an action pursued by Mrs Warner on her son’s behalf was not time-barred.
Mrs Warner, 47, said the last few years had had a “devastating” impact on her and her family.
She said: “The stress is extreme. When my husband died, there were questions asked by solicitors who came back and told me there was a clear case of negligence.
“It got time-barred and couldn’t be heard on my behalf so the only chance was to go to court on my son’s behalf.”
An inquest held in 2014 returned an a verdict of accidental death.
Captain Gavin Pritchard, an inspector for the Marine Accidents Investigation Branch (MAIB), told the inquest Mr Warner’s diving group had not been warned of the dangers of walking on deck in full diving gear.
He said: “There was no evidence of a formal risk assessment of a fully-dressed diver moving from the seated position to the point of entry into the water.
“It was our recommendation to conduct a thorough review of the safety arrangements to minimise risk to divers as they prepare to enter the water.
“The severity of the injuries was such that if he had not dived, his condition would have still reached serious medical emergency level.”
The appeal is due to be heard at the Supreme Court in London on 28 June.
Lawyers for Scapa Flow Charters declined to comment when approached yesterday.