The heartbroken son of broadcaster Brian Black has said he "always knew the ocean would take him", but added that he and his sister are struggling with the nature of their father's sudden death.
Kieron Black and Sarah Brown also said they wished to thank those who tried to save the former UTV presenter's life after his car plunged into Strangford Lough in what they believe was a freak accident.
The 77-year-old grandfather-of-one, who was a familiar face on local television, was in the front seat of the vehicle when it rolled backwards off the quay around 11.30am on Tuesday.
Eyewitnesses ran to the car and used a hammer to smash a window in an attempt to free the well-known naturalist.
Mr Black was airlifted to Belfast's Royal Victoria Hospital, but tragically passed away later the same day.
Cartoonist Kieron (50), a father-of-one, said he was trying to process "the void left by my father" just 10 months after the loss of his mother.
"It was very sudden," he told the Belfast Telegraph.
"The process of grieving hasn't really begun yet... it's still a shock.
"My dad loved the sea and he loved sailing.
"For some strange reason I always knew that the ocean would take him, but I didn't think it would be in a car off the quay."
He told how Sarah (46), who works for a charity, and her husband Colin travelled home from Scotland on Tuesday in the aftermath of the tragedy.
And he said it was hard to believe they were preparing for another funeral so soon after the death of their mum Lesley at 76.
"We lost mummy to lung cancer in September last year, so Covid was an extremely difficult time for dad," he explained.
"Lockdown became almost unendurable for dad.
"He was shielding, he was widowed, he was grieving, he was alone. It was a terrible time.
"It's just so ironic that we got him through that and then something like this happens."
Killough native Kieron, who was on holiday in Portnoo with wife Yulia (42) and their seven-year-old daughter Penny (Penelope), said he last spoke to his dad at 10am on the morning of his death.
"Our wee family were taking a week away and we'd borrowed his camper van," he said.
"We had some issues with the sink so I gave dad a shout and we were chatting, just shooting the breeze.
"It was very poignant because I've just had a cartoon published in Private Eye and my dad, who had an issue in front of him, said he couldn't see it.
"Turns out he was looking at the one with the royals on the cover, whereas my cartoon is in the one with Boris Johnson on the cover... and I told him I'd show it to him when I got home.
"Unfortunately, I never got the chance."
He revealed that his sister broke the news that their dad had died, but that was only after he'd received a confusing text "that made no sense" earlier in the day from a friend who'd heard about the accident.
"Shortly after that I got a message from Sarah saying she needed to talk to me as soon as possible, and then I knew something bad had happened," he added.
"That's when I learned dad was in the Royal and things weren't looking great.
"We immediately began driving and we were just crossing the Donegal mountains when we got another phone call from Sarah saying my dad had passed.
"We had to take a moment. It was a very difficult situation."
He said his dad, who was at the quay as he was planning to sail to Scotland in his boat to visit Sarah, who lives in Argyle, was the victim of a terrible accident.
"From what we gather there was a problem with the handbrake and he was wrestling with that when the car went into the water," he explained.
"There's CCTV of the event. He got out of the car for reasons unknown and got back into the car as it began to roll, and then he was taken into the water in the driver's seat.
"The car landed on its roof and then settled driver's side down.
"They tried to get him out by smashing the windscreen on the passenger's side and held his head above water. But he'd already lost consciousness at this point and he never regained consciousness.
"They got a heartbeat going at the scene and then he was airlifted to hospital, where he died."
Penny, who had a very close relationship with her grandad, has been inconsolable since.
"Dad was a huge part of her little life, especially after mummy died," said Kieron.
"The three of us used to go climbing together and dad took her to pony club every week.
"We took Penny there on Wednesday, her day to go riding, and dad's absence was palpable.
"The fact that he wasn't there was very hard on us."
He told how he and his dad shared a love of the ocean and sailing, and said he will really miss "just talking to him".
"We were only really learning how to grieve for mum and now this," he added.
"Losing one parent and then the other... the axis moves once more. We're adrift at the moment. We're just lost."
A private family funeral will take place on Monday.