Despite efforts to revive Ferry, she died at the scene, police said.
An abandoned World War Two bunker at Bluefish Point, North Head. Photo / Manly Daily / Supplied
Insp Byrnes said the two women were friends and both Northern Beaches locals.
"Our thoughts go out to the family, it's a very sad accident," he said.
Insp Byrnes said Ferry's body was retrieved by a police rescue crew and taken from the area by the Westpac Rescue Helicopter.
COMMUNITY 'DEVASTATED' BY THE LOSS
Ferry was a renewable engineering student at Sydney's University of New South Wales and was recognised on the 2019 Dean's Honours List.
She had travelled to Norway and Sweden for an immersion program in September last year.
"The huge array of people we were introduced to really broadened my perspective on what life could be like once I actually leave university," she said in a video posted to a student Facebook group.
"All the amazing people we met were so humble and they were so willing to share their life stories, and how they had gotten to where they were, it was really great."
Annika Ferry died on Sydney's Northern Beaches in what police have described as a very sad accident. Photo / Facebook
She said she had been inspired by the start-up scene and motivated "to do something meaningful" with her life.