Officers are appealing for witnesses and information after a man "fell from height" at Brighton Marina.
Emergency services attended the incident which happened shortly after 10am on Saturday, December 31.
A 56-year-old man was tragically declared dead at the scene.
His next of kin have been informed.
Police are preparing a report for HM Coroner, and have appealed for witnesses or anyone with relevant CCTV or information to come forward.
Information can be reported to Sussex Police online or call 101 and quote serial 342 of 31/12.