A man is being treated at hospital with serious injuries following an alleged assault at a bar in Butlin's, Bognor Regis.
Police are investigating the incident which occurred in a bar area of the holiday resort just before midnight on Friday (June 14).
During an altercation a 52-year-old man from Bedford was assaulted, leaving him with serious injuries, police have said.
The man is currently being treated at the Royal Sussex County Hospital in Brighton.
A 31-year-old man from Wandsworth, South London, was arrested on suspicion of causing grievous bodily harm with intent and later bailed until July 13 pending further enquiries.
A spokesman for Sussex Police said: "Anyone who saw what happened or who may have other relevant information is asked to contact Sussex Police online at https://www.sussex.police.uk/contact/af/contact-us/ or by calling 101, quoting Operation Brockton.
"Alternatively they can contact the independent charity Crimestoppers anonymously, either via its website www.crimestoppers-uk.org or by phoning 0800 555111."