Missing 21-year-old Sophie Smith is believed to have entered the sea at Gorleston and, consequently, police have confirmed they will be conducting further coastline searches this afternoon.
Officers have sought expert analysis of tidal movements and this information will be used as the coastguard and a police helicopter scour the coastline today.
Inspector Will Drummond said: 'Sophie had been receiving treatment for depression and anxiety. Our enquiries have revealed there's been a degree of pre-planning to her disappearance and this, combined with her mental state and comments made the previous day, suggest the most likely scenario is that she has gone into the sea.
'The sea searches will be carried out by the coastguard while the police helicopter is being deployed to conduct coastline searches. Based on tidal analysis, the searches will be carried out in targeted areas.'
The UEA student disappeared from home in Avondale Road in Gorleston in the early hours of Boxing Day morning wearing only a vest and shorts.
She had been suffering from severe anxiety and depression and left home at 3am without her mobile phone.
She was captured on CCTV a short time later heading towards the seafront but there have been no other confirmed sightings since then.
Insp Drummond added: 'Local CCTV footage has been examined but unfortunately Sophie is not captured on any other cameras. She didn't take her mobile phone and hasn't accessed her bank accounts or social media accounts since leaving home.
'This is clearly a very distressing time for her family and we continue to keep them updated of ongoing work in this case.'
Two small groups of people could be seen searching Gorleston seafront this morning, despite a search organised by a member of the public being called off due to the inclement weather.
Sophie is described as being white, about 5ft 8, of a slim build with shoulder length blonde hair. It is believed she was wearing a dark coloured vest top and light coloured shorts.
Anyone with information should contact Norfolk Police immediately on 101.
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