The $40,000 dock, jointly paid for by the council and the Ministry for Primary Industries (MPI), would allow council staff to treat vessels found with marine pests such as undaria, Mediterranean fan worm and sea squirts on their hulls, biosecurity manager Richard Bowman said.
It could also be used to contain oil leaks.
Once inflated, a vessel suspected of harbouring marine pests could be floated inside the walls via, a collapsible rear ''gate''. When it was completely contained within the walls of the dock a chlorine compound was added, which killed marine pests in 12-24 hours.
The dock's major advantage was its mobility, meaning vessels could be treated ''on the spot'' in the water rather than having to be lifted out, Mr Bowman said.
''Spot checks'' were already carried out on yachts, recreational motor boats and fishing boats in Fiordland two to three times a year, and Mr Bowman said having the dock would enable more regular checks to be carried out.
It could also be used at Bluff to clean boats which were intending to travel to Fiordland, he said.
''We won't be using it every day - probably just in emergency situations.''
The cost of treating boats would be met by owners, he said.
Mr Bowman said the inflatable dock was the largest in New Zealand and could accommodate a vessel up to 20m long. It also came with a large inflatable work platform.
When the equipment was unveiled at Bluff recently, on hand to learn how to inflate it, deflate it and repack it into its large carry bags were Environment Southland and Southport staff, an MPI representative.
Also on hand was manufacturer John Booth, of Taihape-based company Incept Marine.
Mr Booth said his company began 28 years ago making water rafts and started producing inflatable docks about five years ago, mostly for the Australian recreational market.
Boat owners had discovered mooring their vessels inside an inflatable dock at a marina protected the hull from marine pests, leading to reduced hull maintenance, he said.
Inflatable docks now accounted for about 20% of his business, he said.
