A group of sea cadets - boys and girls aged 13 to 18 - will sail from Nelson to Fiji on a 20m yacht to provide aid and collect plankton for international researchers.
Members of the TS Talisman Sea Cadets - boys and girls aged 13 to 18 - will become "planktonauts", collecting plankton using a special sampling kit they will take on their mission.
They will also log environmental data including water temperature, salinity, wind speed and direction.
They have been training as 'planktonauts' with Nelson-based scientist Xavier Pochon of the Cawthron Institute, who is part of the international programme called Plankton Planet which receives samples taken by citizen sailors around the world.
"We've catalogued thousands of plankton species, but since the ocean is so vast and underexplored, there's a real possibility Milo and his crew might discover new species," Dr Pochon said.
"It generates half of the oxygen we breathe, helps regulate our climate, and is a key indicator of climate change. Plankton is also the basis of the entire ocean's food chain."
The sea cadets' unit commander, Lieutenant Milo Coldren, said the voyage from Nelson to Fiji was also a chance for the cadets to learn more about themselves.
"They've got a tough enough time just trying to figure out who they are in life as a teenager, and for the opportunity to be able to do this project with Cawthron and Plankton Planet - it will help create an awareness and a discovery for the cadets of who they are in society, and in the world as a whole," he said.
Lieutenant Coldren said the sail training programme - which has had crews of young cadets tackle the high seas over the past few years - was inspired by what he gained as a young sailor.
"I grew up on the West Coast of Vancouver Island and there was a Kiwi who owned a yacht who let me on to his racing team. He gave me a chance and I did a lot of growing up through that, so being able to reciprocate - it's quite humbling," he said.
Lieutenant Coldren said up to eight cadets and crew would leave Nelson in late June on a 20-metre yacht, and would stop in Auckland before the 10-day voyage to Fiji.
In Auckland they will take part in a Plankton Planet youth outreach project at the Maritime Museum. The six-day workshop, organised by Dr Pochon, will feature international researchers who will talk about the work being done with the help of the planktonauts.
There would also be a public event at the New Zealand Maritime Museum in Auckland at 6.30pm on Thursday 6 July.
Lieutenant Coldren said the cadets taking part needed at minimum a Boatmaster certificate or to be in the process of gaining the qualification, as well as a VHF radio operator's licence.
He said on arrival in Fiji they would spend a couple of weeks on aid work before flying back home.