This rare phenomenon saw an army of the native aquatic arachnids creeping into oyster farms, while in the area to moult.
“Thirty years I’ve been oyster farming here I’ve never seen this many,” Coffin Bay oyster farmer Lester Marshall said.
The creatures, which are capable of growing up to 70 centimetres wide, embark on a remarkable journey, travelling hundreds of kilometres from outside the continental shelf into Coffin Bay.
The deep-sea crabs are typically solitary, but have congregated in shallower waters, piquing the interest of researchers.
“They’re coming into moult and we think they come in and aggregate for protection because when they moult they’re quite soft,” marine researcher Rachel King said.
Victoria’s Port Phillip Bay is the usual hot spot for spider crab displays.