For Lisa Skelton, an Imagine Cruises deckhand who caught the huge mammals in motion, it was the best way to start a rainy Saturday.

“People like me who work on boats probably see it once or twice a season, but for a lot of people it would be a once in a lifetime sort of thing,” Ms Skelton said. 

She estimated the two whales were about 15 metres long and weighed in at 40 tonnes apiece. 

“Scientists don’t know why they breach, but in this case it just seemed to be a social activity,” Ms Skelton said. 

“The juveniles tend to be a lot more inquisitive but this time of year when we’ve got a lot of competitive pods heading north. The males can be quite boisterous trying to impress the females.”

Whale numbers have “exploded” in the past week, Ms Skelton said, as the tourist season begins to hit its stride off Port Stephens and the Hunter coast.

Newcastle Herald reader Michelle Hogg also caught plenty of whale activity off Swansea, capturing several breaches about three nautical miles off shore.

Humpbacks are migrating north at the moment, seeking warmer waters to breed for the season. 

They migrate south later in the year once their calves are strong enough to deal with the frigid southern waters.