Volunteers are using two boats to guide the 17 pilot whales that were stranded at Golden Bay on Sunday morning to the rest of the their pod and try to coax them out to deeper waters, the New Zealand Herald reported.

The whales who refloated themselves late Saturday night were now swimming east towards Collingwood, beach authorities said.

Volunteers discovered that the whales had successfully got back into the water when they went down to the beach to continue their rescue effort, a senior official said.

The group were from a different pod to the 416 whales that were stranded on Thursday night.

Seventeen were still stranded on the beach - 8km further into the bay than where another group were found on Thursday - on Sunday morning.

The environmental group Project Jonah, which is assisting with the rescue, has a plane flying over the bay to keep track of the whales' movements, the BBC reported.

It is not clear why the whales continue to arrive on the 5km-long (three mile-long) beach next to Golden Bay.

Herb Christophers of New Zealand's department of conservation told the BBC that the whales were trying to get round the top of South Island, but if their navigation went wrong they ended up on the beach.

In the shallower waters, the animals' use of echo location was impaired.

"It's a very difficult place if you get lost in there and you are a whale," he said.