A student, who has been missing since Boxing Day, had told her family of her intention to take her own life police have said.
Sophie Smith, 21, left a note to her family "outlining her intentions", before leaving her home in Gorleston, near Great Yarmouth, Norfolk, at around 3am on 26 December.
The University of East Anglia student, who was wearing just a vest and shorts when she left her home, did not take her phone with her and has not used her bank or social media accounts police reported.
She was spotted on CCTV on the morning of her disappearance, when she was seen running towards the beachfront.
Sophie had been receiving treatment for severe anxiety and depression and had previously spoken about ending her life in the sea.
Inspector Will Drummond told Sky News: "We know from speaking to her family that Sophie had previously spoken about her intention to enter the sea to take her own life.
"Sadly, we can also confirm that Sophie had left a note and messages for loved ones, outlining her intentions."
Since her disappearance local volunteers and police have been searching the coast for any trace of Sophie, while 28,000 people joined a Facebook site to circulate details of the student in a bid to locate her.
In a statement Sophie's parents said that while they hold out hope that she may yet be found, they now "fear the worst."
Sophie's mother Lynn Shaw said: "Sophie's step-father Kevin and I would like to thank the public and police for their continued support and dedication in searching for Sophie.
"In our hearts we hold every hope she will return safe and well. However, as a family, knowing the troubles she was experiencing, we do fear the worst for our little girl.
She urged anyone suffering anxiety or depression "not to fight that battle alone and seek help."