Whale numbers off Sydney's coast have recovered so strongly since 2000 that experts estimate 3000 to 20,000 will pass this winter, supporting a lucrative tourism industry.
Compared to the 294 seen in 2000, there are now so many that many whale-watching companies feel confident offering sightseers a refund if tourists don't spot a whale, or a free trip until they do.
This has turned whale watching into a big business for Sydney, said to be the best city to view whales because they come close to the harbour, even entering it at times.
According to Richard Ford, the owner of the first whale watching business in Sydney, its spotting rate was 97 to 98 per cent.
On Friday tourists saw pods of humpbacks and dolphins within 500 metres of North Head. Last week they spotted a sperm whale and her baby, a species rarely seen so close to land.
As many as 3000 whales are seen during daylight hours by the National Parks staff who track their numbers. Other organisations say perhaps as many as 20,000 pass - many at night or without being seen.
Mr Ford attributed the rise to the ending of commercial whaling in Australia in 1978.
Whales supported 19 tour operators in Sydney plus a boat "in every inlet along the coast," Mr Ford said. In 2008, more than 25,000 people took a tour. Since then, some operators have doubled capacity.
When Adventure Cruises began in 2011, managing director John McPherson said the company took out 3500 people. Last year, it had 14,500 customers.
Statistics by the International Whaling Commission say the value of whale tourism is $2.1 billion worldwide, dwarfing that of whale hunting at about $300 million.
Whale Watching Sydney commissioned a study by Macquarie University which found that whales were more likely to remain on or around the surface when vessels were nearby.
Mr McPherson and Mr Ford said the biggest threat was from recreational craft, which sometimes came too close. "A lot of people get so excited that they have to come in close to the whale, which is very, very wrong. They're going north to mate and have babies. If we start hindering their natural habits, it will have an effect," said Mr McPherson.