International help sought for lost whale calf (Credit: ABC News)

New South Wales Premier Morris Iemma says experts are seeking international help for the whale calf stranded off Sydney's northern beaches.

The humpback calf has been trying to suckle off boats moored in The Basin at Pittwater after becoming separated from its mother several days ago.

Experts believe the calf has not eaten since Friday and may beach itself as it moves towards shallow waters.

Mr Iemma says everything is being done to try and help reduce the whale's suffering.

"Everyone's working very hard to try and save the whale and [to see] if we can obtain assistance from international agencies," he said.

"National Parks and Wildlife are doing everything they can. They've been in touch with other marine experts.

"We do have grave concerns for the health and safety of the whale."

Sydney yacht owner Peter Lewis woke up to find the whale underneath his yacht this morning.

"I've been sailing back from Port Stephens and came in late last night and came in to a strange sucking sound on the bottom of the boat," Mr Lewis said.

"It sounds like someone with a great vacuum cleaner trying to suck the bottom of the boat.

"But I realise now the whale must be sick or something, it's sort of limp."

Success story

Dave Koontz from Sea World San Diego in the United States says a team of veterinarians managed to save a baby grey whale which became stranded in 1997.

He says the whale was hand-reared back to health before being released into the wild 14 months later.

"Our veterinarians and our animal care teams immediately went to work to try and save the animal, " he said.

"They were not necessarily optimistic at first just because she was in such a dire condition.

"However, they were able to develop a substitute baby milk formula for a grey whale and in a few days she began to eat and quickly began to put on weight and recover."

Meanwhile, Sea World on the Gold Coast says it is helping the New South Wales Parks and Wildlife Service as it attempts to care for the abandoned whale calf.

A theme park spokeswoman says flying the five-tonne animal to the Gold Coast for treatment is not an option.

Sea World says no decision has been made on whether to rescue the animal.