A Perth beach was closed when a four-metre great white shark was spotted dining on a whale carcass about 100 metres from the shore.

Floreat Beach was closed on Tuesday morning after Surf Life Saving WA (SLSWA) was called to the shark sighting.

SLSWA beach services coordinator Matt Du Plessis said the large shark, thought to be a great white, was between 100 metres and 200 metres offshore.

"We had some surfers in the vicinity and some swimmers and just as a precaution we got them to get out of the water," Mr Du Plessis said.

"The chance of being attacked by a shark is really low but you have to take precautions in these situations."

Mr Du Plessis said fisheries officers and beach inspectors were monitoring beaches to the north of Floreat, including Scarborough beach, as some of the carcass continued to float northwards.

He said the local council had towed some of the carcass to shore and was attempting to move part of the carcass off the beach to reduce the risk of attracting other sharks to the area.