A 24-year-old woman was raped under the Palace Pier in Brighton in the early hours of Saturday morning (10 August).
The victim had been on a night out with her sister. She became separated from her sister and two men they had met earlier in the evening in the Oceana night club in West Street.
All four left the club at around 1.20am.
However, some time between 2am and 3.10am the victim found herself under the pier with a man she did not know.
He attacked her before running off towards the Brighton Wheel.
The suspect was described as black, aged in his late twenties, 5ft 5in tall and of average build. He was clean shaven, with short or shaved black hair and spoke with a London accent.
He was wearing black hooded zip-up top, dark jeans and black boot trainers.
Detective Constable Aran Boyt, from Brighton and Hove CID, said: “This was a very distressing end to what was a fun night out in Brighton.
“We need to find the person responsible for this nasty assault as a matter of urgency.
“Officers will be continuing with local inquiries and viewing CCTV from the area in a bid to trace the victim’s movements after she left the company of her sister and the other two men.
“If you have any information, no matter how irrelevant you think it is, please get in touch.
“I would also like the two men who the sisters left the night club with to please get in touch as I believe they may be able to help us trace the victim’s movements prior to the rape.”