"It's amazing to see how much momentum and awareness this issue has grown back in New Zealand as well."
For him, the importance of protecting the world's oceans was evident once he learned the stats: they produce half the world's oxygen and absorb more than 90 per cent of the heat.
He said New Zealand was lagging behind others when it came to ocean protection.
This included the amount of Marine Protected Areas and the "archaic" ways the ocean was harvested.
"It's really just understanding what the ocean does for us and how quickly it is changing."
That understanding was what fuelled his passion for action, he said.
He acknowledged he spent a lot of his time on the ocean, but said it was a big part of many other New Zealanders' lives too.
He and Tuke will take the declaration to the UN leaders with other leading local and international sports people and ocean voices this weekend.
It was launched at SailGP's Chicago Grand Prix last weekend.
Called the Live Ocean Voices for a Healthy Ocean declaration, it has been signed by former Prime Minister Helen Clark, master navigator Hoturoa Barclay Kerr and Lady Pippa Blake as well as sports people from Jo Aleh, Sam Cane, Mahe Drysdale and Gustav Legnavsky to John John Florence, Ana Ivanovic, Jimmy Spithill, Ricardo Christie and Hannah Mills.
The declaration describes how the ocean is a gigantic carbon sink and a powerful tool against climate change.
"But it's heating up, becoming more acidic and is at a tipping point. The connection between the ocean and climate is clear. To have a healthy planet, we must have a healthy ocean."
Those who signed declared to commit to start conversations, raise awareness and share stories for environmental outcomes.
The conference, hosted by the governments of Kenya and Portugal, will run from June 27 to July 1 in Lisbon and will be attended by heads of government and state, together with leaders from the private sector and the scientific community to look at how to protect and conserve the ocean and its resources.