Diesel from a semi- submerged oyster boat in Foveaux Strait has been contained.

Divers plugged air vents in the fuel tanks of the Torea yesterday, which had been seeping diesel since the boat - with 23 people on board - hit rocks on Friday.

Environment Southland's Dallas Bradley said a 10-metre slick of diesel had seeped from the Torea's air vents, but it was being "carried offshore by the wind and was dispersing naturally in choppy seas".

The Torea was sitting on the seabed, with most of the deck underwater, and was holding about 2500 litres of diesel.

Environment Southland had been liaising with the Department of Conservation and iwi about the potential impact on the environment and wildlife, he said.

However, there were no concerns the diesel had caused problems, Bradley said.

"Now that the air vents have been plugged, the focus will shift to salvaging the vessel."

Responsibility for salvaging the vessel was with the Torea's owner and insurer, he said.

"Our ongoing interest is to ensure that there is no spillage of diesel from the vessel during the salvage," said Bradley.

The boat's owner, Campbell Town Seafood, declined to comment.

The Torea had been chartered for a fishing trip when it started taking on water. Skipper Peter Leask, who had 23 passengers and two crew on board, steered to nearby Ruapuke Island.

A dinghy ferried everybody onto Ruapuke from where they were rescued.

- © Fairfax NZ News