The car became stuck in an area in Bucklands Beach just after 9.30pm.
Police said last night the people inside the car at the time of the incident included two children - whose ages have not been released - who were safely removed from the vehicle by a member of the public.
It is understood an adult was taken to hospital.
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A woman, Megan Holt, said on a community Facebook group last night that she was one of the first people on the scene.
"My partner rescued three people. We went into water [and] were told no one else in car. Not sure what type - just reacted," she said.
"A man has been taken to hospital. I'm just grateful the children are okay''.
A cordon that was in place on The Parade - between Whitcombe and Laings Rds - has now been lifted.