Sharks force closure of WA and NSW beaches

About 100 people rushed out of the water after 15 sharks were spotted metres from shore on the NSW south coast.

Life savers sounded an alarm and ordered people out of the water at Hyams Beach in Jervis Bay just after 2.30pm.

Two larger sharks were shepherded out to sea but about 12 smaller ones remained about "two or three paces" into the water, a Westpac Life Saver Rescue Helicopter spokesman told AAP.

Two life savers will begin patrolling the area for two weeks starting on Friday.

A shark sighting also forced the closure of a West Australian beach on Thursday afternoon.

Surf Life Saving WA closed Meelup beach, in the state's South West region, after a 2.5 metre shark was spotted about 50 metres offshore.