Scuba divers off the Californian city of San Diego are being menaced by large numbers of jumbo squid.
The beaked Humboldt squid, which grow up to 5ft (1.5 metres) long, arrived off the city’s shores last week.
Divers have reported unnerving encounters with the creatures, which are carnivorous and can be aggressive.
One diver described how one of the rust-coloured creatures ripped the buoyancy aid and light from her chest, and grabbed her with its tentacles.
“I just kicked like crazy,” diver Shanda Magill told the Associated Press news agency.
“The first thing you think of is: ‘Oh my gosh, I don’t know if I’m going to survive this.’ If that squid wanted to hurt me, it would have.”
The creatures – also known as jumbo flying squid – do not affect swimmers because they remain deeper in the water.
But dozens have been washing up on beaches in the area.
“The ones that we are getting right now have a big beak on them, like a large parrot beak,” San Diego’s Union-Tribune quoted John Hyde of the National Marine Fisheries Service as saying earlier in the week.
“They could take a chunk of flesh off you.”
Diver and amateur underwater cameraman Roger Uzun said he swam with a group of squid for about 20 minutes.
They seemed curious about him, he said, and appeared to be touching him and his wetsuit with their tentacles to see if he was edible.
“As soon as we went underwater and turned on the video lights, there they were. They would ram into you, they kept hitting the back of my head,” he told AP.
It is not the first time the squid, which can weigh up to 45kg (7 stone), have taken up residence off California’s coast.
In January 2005 hundreds of them washed up off the coast of Orange County, to the north, and in 2002 a similar invasion was reported near San Diego.
Scientists say they do not know why the squid – which usually live in deep waters further south off Mexico and Central America – have come so close in.
But one expert, Nigella Hillgarth of the San Diego-based Scripps Institution of Oceanography, told AP it was possible that the squid had established a year-round population off California.