The survey is like mowing a lawn, traversing back and forth mapping the lakebed below. Photo: Kate Green / RNZ
The Navy has descended on a Wellington eco-sanctuary - but it's not to prevent an invasion, pests or otherwise.
Rather it is conducting a survey of the Zealandia lake, good practice for the crew and useful information for the sanctuary.
Zealandia chief financial officer John Diggins watched on while the Navy crew set up their black, inflatable Zodiac with surveying equipment on Wednesday morning.
"It's really exciting," he said. "It actually shows us how the lake sits underneath, you can see the old creek that runs through, the original creek from before the dam was actually built, and just shows us any submerged logs.
"There's also potentially a little goldmine down there, a little goldmine shaft that they saw on the last survey."
The Navy crew sets up their surveying equipment aboard the Zodiac on Wednesday morning. Photo: Kate Green / RNZ
That survey was done in 2018, and since then, technology had advanced and would hopefully give them a better look.
The results would make it safer to navigate Zealandia's electric boat, Ara Kawau, around the man-made lake, Diggins said.
"It's a really cool trip, and it's just really good to know if there are submerged logs that are hazards for the boat so we can just stay away from them."
The Navy crew would be on deck for the next couple of days, and Diggins hoped they might get time to map the Upper Dam as well, which had never been surveyed before.
Chief petty officer Julie O'Hara of HMNZS Matataua and the Navy's search, survey and recovery team. Photo: Kate Green / RNZ
Chief Petty Officer Julie O'Hara of HMNZS Matataua and the Navy's search, survey and recovery team explained the portable multi-beam surveying system could see down to depths of 300 metres - but she was not expecting anything deeper than 15 metres.
Three crew members set out across the lake in the Zodiac just after 10am. The boat would traverse back and forth across the lake, mapping the floor below.
"It's kind of like mowing the lawns," O'Hara explained.
The end product would come in the form of a map, with different colours representing different depths, which Zealandia could use to steer clear of shallows and obstacles - and it could be ready as soon as Friday.
Zealandia's chief financial officer John Diggins watches on, as the Navy crew sets up the boat for the lake survey. Photo: Kate Green / RNZ
As well as being useful for Zealandia, O'Hara said it was good training.
"We had a bit of an operational pause at the start of the year from the Manawanui sinking [in October 2024], so we came together as a trade and looked at how we can improve."
"A lot of training, getting back into it, and then doing this training exercise here to really consolidate it."
Zealandia's electric boat, Ara Kawau. Photo: Kate Green / RNZ
The team carried out a huge variety of work - uncovering landmines, recovering vehicles, searching for missing people and surveying sea floors.
"We never know where we're going to deploy in the world, and what's asked of us, so by doing different lakes it really gives us the training that we need to move from normally working salt water, to working in fresh water."
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