An oil spill from a tourist boat that sank in Doubtful Sound in Fiordland on Thursday night is a safe distance from environmentally sensitive areas, says Environment Southland.
There are fears that up to 700 litres of fuel could spill from the Waverly, a tourist boat that hit a submerged object about 9.30pm.
The eight passengers were rescued before the vessel sank just after midnight.
Environment Southland spokesperson Michelle Poole says the spill is a kilometre wide.
Ms Poole says the oil slick is at least five kilometres from the nearest marine reserve and 10 kilometres from the nearest known breeding grounds for the Fiordland crested penguin.