The Bay of Plenty Regional Council has no explanation as to why after-hours calls made on Monday night in relation to a sinking boat went unanswered.

Bruce Galloway saw a launch sinking in the harbour between 8.30-9pm, but was unable to raise the council harbourmaster when he called.

The boat sank about 14 hours after a neighbour tried to raise the alarm.

He then rang the Tauranga Volunteer Coastguard, which went through to Coastguard Northern Region, who were also unable to contact the harbourmaster.

They advised Mr Galloway to call again the following morning.

BOP Regional Council communications partner Prue Sisam says Bruce's call was logged at 7.50am on Tuesday morning and was passed onto the Maritime team by 8.01am.

At 8.05am the Deputy Harbour Master had responded.

'We are currently investigating whether there were any issues with calls being received by the call centre the previous night,” says Prue.

'Once we know if there were any issues and what caused them we will let you know what we're doing to prevent them happening again.”

When Bruce first called the regional council, the moored 10.9m launch was still afloat. It was still floating when he called on Tuesday morning, but the water was up to the gunnels.

However, it had sunk by the time the regional council got to it.