Australian boaties have been urged to remain vigilant after three people aboard a speedboat collided with a whale and its calf south of Sydney.

Troublesome vision was captured of a southern right whale and its calf south in waters off Stanwell Park on Saturday afternoon.

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The pair were swimming just beneath the surface when they were hit by the boat.

It is understood both the whale and calf escaped without major injuries.

The whales have just begun their annual migration and will continue travelling north this week.

The mother was first detected off Bass Point on June 12 without the calf, and then near Meriumbula on July 10 with her baby.

Whale expert Dr Barry McGovern from Pacific Whales Foundation said southern right whales often stay just below the surface and can be very hard to spot.

“They also don’t have dorsal fins like your humpback whales so they can be really difficult to see and if you’re travelling at speed it can be very easy to miss them, to not see them,” he said.

“The larger boats can really impact them.

“Whales can suffer some serious injuries from vessel collisions and in some cases they can be fatal, particularly with the larger vessels.”

He urged any boaties off Sydney’s coast to stay vigilant and said the best thing to do is to slow down if they are travelling through the area.

“If you’re in an area where you know there are whales, or people have seen whales previously, it’s best to keep it slow,” McGovern said.

“If there’s whales below, keep it slow — that’s what we always say.

“Our research has shown boats (that) are travelling less than 12 knots, which is about 22km/h, there’s a much lower chance of hitting a whale.

“It allows you to see if the whales are there in the first place and even if there is a collision, at the slower speeds, the injuries are less likely to be as severe.”

There is an exclusion zone of 300m for whales with calves, and 100m for whales without newborns.

This not only applies to vessels in the water but also drones in the air.

“While seeing one in Sydney is exciting, it’s important to remember that this whale and her calf must be given space and quiet as they travel north,” NSW National Parks and Wildlife Service (NPWS) ranger Natasha Funke said.

“Southern right whales rely on sheltered coastal bays to rest and feed their young, and they need to do this without interference, so we encourage people to enjoy this spectacle from land or a safe distance on the water.”

A list of national park viewing spots to watch the whales as they migrate is available on the NPWS website.