The Southland Regional Council says divers are expected on Saturday to inspect two vessels that sank in Fiordland.
The vessels were moored together and sank at Beach Harbour in Breaksea Sound on Friday morning.
A regional on-scene commander, Dallas Bradley, says the owner has arranged for divers and salvage company crew to fly to the site.
He says while a small amount of diesel has made its way into the water, it is naturally dispersing due to strong winds.
Mr Bradley says no-one has been on two vessels for several weeks and why they sank is unclear.