Swimmer reported missing off Sydney beach

A search is underway for a swimmer reported missing off Maroubra Beach in Sydney's southeast.

Police were called to the northern end of Maroubra Beach about 8pm on Tuesday after reports a swimmer was struggling in the water.

A witness told police the swimmer appeared to be 50 metres from shore.

Police are conducting a search of the beach with the assistance of a rescue helicopter.

Anyone who was in the water between 7.45pm and 8.15pm is being urged to contact police immediately.