Boaters are being urged to keep a lookout for an injured whale last seen entangled in ropes off Sydney's Bondi Beach after a wide-scale air and sea search was called off.
There have been no sightings of the 10-metre humpback since it was spotted by a whale-watching boat on Tuesday afternoon, when crew from that vessel managed to cut some of the ropes off.
The crew used a makeshift knife duct-taped to a long pole to achieve the task, but had to leave before the animal was entirely free, due to fading light.
Official search crews spent Wednesday resuming the search, with NSW National Parks and Wildlife Service saying finding the sub-adult mammal had been "like trying to find a needle in a haystack".
NPWS spokesman Lawrence Orel said on Thursday they will now rely on eyewitness-reports to find the whale, believed to be somewhere between Sydney and the Central Coast.
Usually, the prognosis for any marine fauna entangled in ropes is not good, but NPWS remains optimistic.
"Given some of the material was cut on Tuesday afternoon, (it is possible) that the remainder may have been able to come off the animal," Mr Orel told AAP.
The annual migration of humpback whales involves about 30,000 animals making the trip north to breed and is one of the largest wildlife migrations on the planet.
Mr Orel says the migration number is excellent, considering the whale population dropped to an estimated 500 before Australia banned whaling in the early 1960s.