Milford Sound's Underwater Observatory in Harrison Cove has partially sunk following a significant weather in the area last week (1 Sep).

Owned and operated by Southern Discoveries, the tourist attraction was opened in 1999 and allows visitors to view the fjord's fish and underwater plant life including a rare species of black coral normally only found at 500m in the open ocean.

The Observatory consists of five interconnected pontoon networks.

Photo: Southland App

Southern Discoveries CEO Kerry Walker said the observatory had been closed for scheduled maintenance at the time and nobody had been on-site when the main building had partially submerged overnight on Sunday, 1st September.

Initial assessments show that the underwater chamber and kayaking pontoon are unaffected, while the main reception area pontoon has partially submerged.

The main docking pontoon and generator pontoon are visibly leaning, Walker said.

Southern Discoveries was currently working with engineers to evaluate the situation and determine an appropriate recovery plan.

Walker said this process is ongoing and includes detailed assessment of the structure above and below the waterline, using a team of commercial divers.

The plan includes multiple steps incorporating containing any debris, securing the site, assessing next steps, and establishing a recovery plan.

The initial priority has been to minimise the spread of debris and any potential environmental issues, he said.

Early indicators are that there has been minimal impact on the Sound or it’s wildlife.

Southern Discoveries Underwater Observatory has partially sunk following bad weather at Milford Sound. Photo: Southern Discoveries

A small fuel leakage (less than 10 mls) had dissipated within 30 minutes or was captured in debris socks around the site., Walker said.

Work has been carried out securing the site including on the link arms holding the pontoons in place.