The Maritime and Coastguard Agency said five people had to be rescued after the incident unfolded just after 6pm.
Police and paramedics were called to the scene.
A spokesman said: “HM Coastguard sent Hastings and Eastbourne RNLI lifeboats, Hastings, Bexhill and Eastbourne coastguard rescue teams, Sussex Police and the HM Coastguard helicopter from Lydd.
“People at the beach also went to the aid of the five in the water.
“All were brought safely back to shore and passed into the care of the South East Coast Ambulance Service.”