Australians Lesley and Doug McGrath have for decades battled ocean swells that have eaten away at the backyard of their multi-million dollar Sydney home.

They bought an old beach shack on Collaroy Beach in 1976 and replaced it with a two storey home anchored to the land by 12 meter (35 feet) long piers, a concrete slab, and an underground seawall of giant boulders.