Reports suggest two men were flung into the water after a whale breached close to the vessel,police say.
Ferry passengers enjoyed a free whale watching experience as the inquisitive mammals swam near the Harbour Bridge before turning back towards the open ocean.
Nearly 100 whales who beached themselves off the southern coast of Western Australia have died after the surviving half of the pod stranded themselves again on Wednesday night after being freed.
Dozens of whales have died after more than 70 were stranded on a beach in Western Australia.
Volunteers in kayaks gently herded 45 surviving whales into deeper water,but they returned and beached themselves again.
Rescuers are attempting to release the beached whales at the same time to prevent them re-beaching themselves with the rest of their pod.
It's believed most of the whales that beached at a West Australian beach on Monday afternoon have died overnight. Video credit:9 News Perth/ Sarah Smith.
The 30-tonne humpback whale died at a Lennox Head beach after maritime rescuers spent much of the day scrambling to save it.
The frenzy involved about 50 tiger sharks scavenging a humpback that died of natural causes and was adrift.
A kayaker has been treated to a once-in-a-lifetime experience with a humpback whale swimming alongside them on Saturday morning.
The whale migration season is off to a bumper start,highlighted by the possible return of a whale superstar.