Fewer than 50 litres of diesel and 10 litres of engine oil was spilt into the water around Nelson Quay when a moored vessel was found fully submerged, the Hawke's Bay Regional Council says.
The boat owner said it was capable of holding up to 300 litres of diesel. At the time of its discovery, regional council staff were unsure how full it had been, how much oil had been spilt and how long it had been underwater.
Hawke's Bay Regional Council manager (compliance and harbours) Bryce Lawrence said the clean-up had been successful.
"The staff removed all the booms and absorbent materials on Friday morning and it was a successful clean-up," he said.
"It was less than 10 litres of oil and less than 50 litres of diesel over the course of the entire period."
Despite other boats discharging oil in the harbour from time to time, the council was confident the oil found in the immediate vicinity could be attributed to the sunken vessel.
The boat's owner, Dale Salomonson, said it had sunk on Wednesday night and he was glad there was not more oil in it. He was still unsure about how it had sunk, but thought it was probably weather-related.
He believed there had been 30 litres of diesel, and 4.5 litres of engine oil in the boat at the time, and he was facing clean-up costs.
"It holds up to 300 litres, so I'm glad I didn't have it full because it'd be a lot more money I would have lost, too. There is some oil that has come from my boat, but overall it is just a minute drip that's going in there on a daily basis."