The Kāpiti story of the missing scientific buoy, worth several hundred thousand dollars, has the makings of every good thriller.
A celebrated beginning, a mysterious disappearance, questions of foul play, and now after weeks of searching its recovery offers a glimmer of hope for answers in the third act.
Spoiler alert, it was not a hit and run.
On Friday, April 30, a month after its sudden disappearance, the Kāpiti Coast biophysical buoy WRIBO-K was pulled from the water.
A week prior, a remote-operated vehicle spied the buoy 50m down on the seabed.
It had been measuring water quality on the edge of the Kāpiti Marine Reserve for fewer than five months.
NIWA oceanographer Dr Joe O'Callaghan said its recovery is a huge relief after several attempts at rescue.
An initial inspection suggested the depth and swift currents caused the buoy to sink in challenging conditions for the mooring.
Limited damage to the hull has ruled out any hit-and-run impact by a boat.
"The team certainly designed a mooring for the known strong currents in the region, but visual inspection showed the mooring chain became tangled in the mooring weight, pulling the buoy under the surface over time until it filled with water and sank," O'Callaghan said.
Sensors designed to detect water intrusion were not triggered and so there was no early warning.
"An evaluation of the buoy and instruments over the coming weeks … will determine costs for repairing or replacing damaged components and ongoing feasibility of the project."
The buoy, a joint project of Greater Wellington Regional Council, NIWA and the Department of Conservation (DoC), was a "sister" to one in Wellington harbour.
According to the DoC website the buoys provide real-time measurements on currents and waves, salinity, oxygen and chlorophyll, water temperature, sediment, wind direction and speed.
Technical adviser at DoC Laura Wakelin said capturing data on water quality in different urban locations enables the impact of land activity on marine life to be compared.
She said the Kāpiti buoy had been installed to track changes near the marine reserve as the coast "undergoes rapid urbanisation".
Guardians of the Kāpiti Marine Reserve chairman Ben Knight said it was fantastic that the buoy had been discovered, but he wondered whether the equipment would still be operational.
"We will have to wait until it has been successfully re-floated to see how well the instruments have survived, at what is quite an extreme depth for equipment intended to be near the surface."