The intrepid paddlers departed from Port Welshpool early Monday morning in a double mirage sea kayak and bound for Refuge Cove in what is expected to be at least an 8-day crossing on the high seas to raise money for this year's Albury-Wodonga Winter Solstice.

Family, friends and supporters are praying for calm seas as they navigate the notorious Bass Strait as part of The Paddle For Survivors campaign.

They set sail with enough dried food to last them 15 days, 40 litres of water, safety equipment, tracking devices and decades of paddling experience and friendship.

"Weather is the biggest issue for us - the seas are very cranky down there," Matt said on Easter Saturday ahead of their departure.

"(But) in the double we've got quite a good advantage; in the first days, if the weather doesn't change, we've got enough power for it not to be an epic paddle."

Both men are experienced paddlers but while Matt, 46, has represented Australia on the water and, together with his wife Emma, completed plenty of ocean paddles, he admits "I've never been out of sight of land".

Stuart says there is "no way I'd be paddling across the Bass Strait with me!"

"But I'm confident Matt has the skills to help us get there," he says.

"It will be OK as long as we don't take on conditions that are beyond us."

Matt and Stuart have been busy paddling up and down the mighty Murray River in the months and weeks leading up to this, their greatest adventure together to date.

But Stuart admits "nothing will prepare us for what we find at sea".

And he predicts long hours in the boat will take their toll.

"You get uncomfortable after 2 hours so it will be a grind to spend 7 or 8 hours in a boat every day," Stuart said.

"It's also weather dependent - if the next week gets difficult to paddle, we will have a stopover and could be stuck out on an island.

"A typical trip can take 18 days due to wind conditions and seas that can cut up pretty rough; we want conditions that are no more than 10 knots (15 knots at a pinch) and swells under 1.5 metres."

But at the heart of this adventure is a gritty resolve to make a difference to the lives of the thousands of Australians impacted by mental illness and the grief of suicide; the determination borne from a 30-year friendship and the pain of a daughter lost to suicide.

The journey aims to raise funds to bring to life the Albury-Wodonga Winter Solstice, which Stuart and his wife Annette co-founded in 2013, and support advocacy group Australians For Mental Health.

Matt is a staunch supporter of Stuart and the family's relentless campaign to advocate for changes to Australia's beleaguered mental health system.

"Their journey has been a tough one over the years," he said.

"It wasn't a big leap to take on this trip with that in mind: you have to believe in yourself when you do things out of your comfort zone."