Last winter, a team of divers braved Tasmania's icy eastern waters to help give the region's spectacular giant kelp forests a fighting chance.
Under the waves, the volunteer divers strung lengths of twine adorned with juvenile kelp to the root-like bases of other seaweeds.
It's a restoration technique developed by Institute for Marine and Antarctic Studies scientists over several years that has already been used successfully to repair patches of the towering forests.
Quick and efficient enough to be rolled out at hectare-scale, the technique's proponents are hopeful it can secure a future for the critically endangered marine ecosystems under threat from climate change, nutrient-poor waters and their natural enemy, the sea urchin.
The next step has been recruiting divers - and lots of them - to reseed more forests.
At least 60 divers, many of them recreational, have already gone through a giant kelp restoration training course developed by IMAS and Eaglehawk Dive Centre, a program supported with federal funding.
After learning to identify different seaweed species and the practicalities of reseeding the kelp propagules, many trainees participated in out-planting dives organised on Tasmania's east coast over the winter months.
Eaglehawk Dive Centre dive instructor Pauline Nuttens is hopeful the first round of microscopic kelps planted via the course are growing strongly through the typically fertile spring.
"Fingers crossed, it's going to work," she told AAP.
Students motivated by the perils of climate change have been well represented among the restoration trainees, as have older divers bearing witness to the slow demise of the kelp forests.
It's estimated as much as 95 per cent of eastern Tasmania's once-abundant giant kelp forests have vanished.
Other trained restorers just love diving.
"They just want another excuse to go underwater," Ms Nuttens said.
IMAS ecologist and project leader Scott Ling says "voluntourism" will be key to building the necessary human capacity needed.
"It will be an exciting and unique opportunity for recreational divers to assist with the establishment and ongoing maintenance of giant kelp forests at local dive tourist sites on the Tasman Peninsula," Assoc Prof Ling said.
The recreational diver training is just one pillar of a $3.5 million whole-of-reef-ecosystem project that also involves commercial sea urchin harvesters targeting restoration sites.
Eastern Tasmania's cold-loving giant kelp has been battered by rising global temperatures and the East Australian Current carrying warm, nutrient-poor water south from the subtropics.
Warmer ocean temperatures have allowed the long-spined sea urchin to thrive, a species known for chewing across the sea floor and leaving nothing behind but bare rock.
Giant kelp forests are valued for providing habitat for a range of marine life, including prized commercial fish species such as rock lobster, as well as for their properties as carbon-absorbers and coastline protectors.
Giant kelp also fight for space with other seaweed species and once they start losing their dominance, struggle to muscle out the competition.
As such, successful restoration first involves clearing a small patch of competing species before tying the hatchery-reared juveniles around the holdfast stubs of other seaweeds.
The whole process takes less than a minute, with practice.
Using reef holdfasts has been found to improve survival and attachment rates dramatically compared to other techniques explored by the researchers over the years.
In earlier trials of the holdfast method, the kelp has developed reproductive fronds within nine months and new "self-recruitment" within a year, indicating all-important self-sustaining forest recovery.
