Sussex Police were called to reports of a 'large group of people' at an unlicensed music event in South Portslade last night (July 17) at about 7pm.
Sound equipment was seized by officers and revellers were told to go home, police have said.
A spokesman said there will be a 'strong police presence' across Sussex today (Sunday, July 18).
They said: "We responded to a large group of people arriving at an unlicensed music event in the beach area in South Portslade about 7pm yesterday.
"Access to the location was closed by police under public order legislation and those present were directed to leave. Officers seized sound equipment that had been brought to the location and the event was brought to a safe and timely conclusion.
"Officers attended the beach area near Basin Road South, Portslade at 10.30am today (18 July) and have seized sound equipment to prevent a second unlicensed music event from taking place.
"There will be a strong police presence across Sussex today and we will not tolerate unlicensed events that breach current Covid-19 safety regulations. We will take robust action against individuals where any offences are committed."