Whales breach near popular fishing spots, such as the one off Lighthouse Beach where the couple were casting on their vessel with a friend. 

When they set sail for home and headed towards Bird Rock, they were suddenly rocked by what they initially thought was a pod of dolphins.

"It was about 6.30pm. We noticed what we thought were dolphins about 500 metres away," Ms Slater explained. 

"We slowed down at that point, but as they got closer we realised they were actually whales. All of a sudden I felt the back of the boat lift up and tip to the side. 

"It was basically in slow motion. It wasn't violent, (but) I thought we were going to go all the way over."

As the whale completed its nudge, it was parallel with the side of the boat, and as it sunk back down the boat got sucked down with it. 

"The whale peeled off to the left and shot off," she said.

"We think it was giving us a warning to stay away from its young as there were three whales, two quite small. 

"That is what we figure. If we were in a smaller boat it would have tipped all the way over."

Marine Rescue Camden Haven unit commander, Ken Rutledge, was not fussed when he heard about the incident.

"It doesn't surprise me that something like that does happen because of the amount of whales out there at the moment," he said.

"There are rules in place to stay a certain distance from whales, but you can't tell the whales to keep away. 

"Often some boats will report that they have gross encounters with whales."

Mr Rutledge believes the whales will jump up and show themselves for a number of reasons, but are usually gentle giants.

"They might be curious and they might also be warning the boat. I'm not too sure," he said. 

"But the ocean is their domain. You never know what they're going to do. 

"To be honest I've never really had issues with whales. We see plenty of them when we're out there and they will quite often breach near you. 

"We keep our distance and they usually keep theirs, but this is proof that these sort of things can happen."