A teenager was taken to hospital after having a bottle smashed over his head on the beach in Kemp Town at the weekend.
The 18-year-old, who lives locally, was treated for cuts and bruises at the Royal Sussex County Hospital in Brighton.
The attack happened at about 3.40am on Saturday 8 October.
His attacker hit him on the head with the bottle several times, causing it to smash.
Anyone who saw the incident is asked to contact Sussex Police on 0845 6070999.
Two men from London, aged 18 and 21, have been arrested on suspicion of assault causing grievous bodily harm.
They have both been released on police bail pending further inquiries until Monday 14 November.