A lucky pilot has described hitting the water in his helicopter and being unable to get his seatbelt off.

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Rick Lucas clambered uninjured from his helicopter after it plunged into the Pauatahanui Inlet in Wellington this morning.

He was rescued around 12.15pm after his helicopter ended up 500m east of Moorehouse Point.

Police, ambulance, fire services and the Coastguard successfully plucked him to safety after the craft plunged into the Porirua harbour just after 11.30am.

Lucas spoke to media at the scene of the crash, saying he knew something was wrong when he felt "quite an intense vibration that got worse and worse" before the helicopter began to rotate.

"I just carried out what are considered to be the normal emergency procedures and got away with it."

The pilot said he tried to stop the machine from rotating, but hit the water with a "significant impact".

"I ended up under the water, couldn't get my seatbelt off," he said.

He has flown helicopters for 35 years and has had one other tail rotor failure in his life.

"I'm a little bit sore, but I'm fine," he said.

"It's not a nice feeling. It was bad. And I think the outcome's exceeded my expectations by a long way. The fact that I ended up in the water, unable to get my seatbelt off, got my seatbelt off, couldn't tell up from down until I saw some light and then I was able to head towards the light and then emerged in the cockpit, so I was pretty happy.

"I didn't panic, I almost went into some sort of state that allows you to think logically and consciously. I looked for the seatbelt, found it, released it. I thought my leg was trapped which was my biggest concern."

He had cut the inside of his mouth and damaged his helmet in the crash.

"But I consider myself very lucky . . . I'm just happy."

The national rescue centre ran the rescue operation alongside police, the Civil Aviation Authority, the Transport Accident Investigation Commision and the region's harbour master.

Lucas was assessed by a paramedic.

Coffee cart owner Alex Finney said he saw the half-submerged helicopter about 1km off the shore at Browns Bay in Porirua.

He saw a person standing on top of the downed craft.

A rescue helicopter was circling overhead and two kayakers and a boat was beside the submerged chopper.

A witness said the pilot had managed to land the chopper on a sand bar, where it was submerged in about half a metre of water.

"Only the pilot was in there and he's safe so that's all good news," the man said.

"Some of the water's up to sort of about half way up the window . . . it's landed and it's sitting on its feet.

"The good news is it looks like he's probably going to be okay. I just don't know about his chopper."