Marine experts caring for our largest national park are concerned about a growing threat under the surface.
A foreign and invasive seaweed, known as Undaria, is spreading and there are calls for boaties to be extra vigilant when out and about in the Fiordland sounds this summer.
For the most part the park underwater appears stunning, but for marine experts, some of it is an eyesore.
"It looks like a canopy on top of everything," said Southland's regional council marine biosecurity coordinator, Andrea Faris.
The seaweed originates from Japan.
Environment Southland's Kathryn McLachlan told 1News, "it's ability to reproduce really quickly and establish [itself] allows it to outcompete our native species."
Undaria is commonplace across many of New Zealand's coastlines, with the seaweed washing up in Fiordland National Park about a decade ago.
Rebecca McLeod is from the Fiordland Marine Guardians and said they are "pretty devastated" about the recent find in Tamatea/Dusky Sound.
"That's why we've been putting so much effort in to try and control it," she said.
Environmental organisations had successfully kept the seaweed at bay in Te Puaitaha/Breaksea Sound since it was first discovered in 2010.
But just last month, it popped up further south in Tamatea/Dusky Sound.
"You can see there are thousands, they're all over the place," said Faris.
"The [seaweed] is taking away the light which means a lot of the other plants and stuff that would normally grow up through just can't because they're not getting resources they need," she said.
The government's Jobs for Nature programme has poured $2 million to send divers down to painfully remove each plant - one at a time.
But the funding is running out.
"It will be a little uncertain however we will be working hard with our partners... to best manage this going forward," said McLachlan.
Both the Department of Conservation and Ministry of Primary Industries told 1News in a statement, elimination using the current tools on hand is unlikely.
But they said another method is being trialled to see the seaweed can be suppressed faster and more effectiviely.
Maria Kuster from Pure Salt Charters in Te Anau is part of the team exploring the alternative method and said, "All it is really is a diver prying whatever they are getting off the rock face.
"But, instead of putting the weed into a bag, it goes up the suction dredge to the surface to be dealt with right away."
In the meantime, advocates are urging boaties to be extra vigilant and mindful when out and about this summer.
"This is a really timely reminder for how important it is for owners and operators to be checking their vessels and cleaning them before they go into Fiordland," said McLachlan.
"And if they are moving around some of these areas, that they're aware of where the undaria populations are and that their gear is clean as well."
So Fiordland can continue to be a treasure trove for all.
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