Incredible footage shows 'hundreds' of spider crabs near Cornwall beach in St Ives
Cornish diver Kate Lowe captured the phenomenon
Spider crabs have been spotted across the Cornish coast, preventing some people from entering the water.
The crabs gather in large numbers for protection at this time of year but have been forming particularly large clusters this year due to hotter temperatures.
As they shed their old hard shells, their new shells are soft, making them vulnerable to predators. Like gulls, they gather together in shallow water for safety.
Marine photographer Kate Lowe wants to inform people that the crabs are harmless, despite recent reports suggesting otherwise.
She spent time carefully snorkelling with the crabs, taking footage of the creatures.
She said: “We arrived at Porthgwidden beach in St Ives last week at low tide to see a large dark patch under the water which we initially thought was rocks and seaweed.
“As we got closer, we realised that it was hundreds of spider crabs, we put on our snorkel gear, were very careful not to step on the crabs as we were entering the water and spent about an hour floating above them on the surface. It was an incredible experience.
“I often snorkel in our local area and see individuals and occasionally small groups but this is the first time I was seen such a huge number of them. The crabs are harmless to humans and it was amazing sharing the water with them” she finished.
Experts say that while mass gatherings of the crabs are not unusual in the UK, they are becoming more common. There is no data to suggest why this is yet.
"We're really privileged to be able to see these large crabs congregating in shallow waters around the Cornish coast" said Matt Slater, Marine Conservation Officer at Cornwall Wildlife Trust.
"They're coming into these sheltered areas in large areas, to moult and to breed, it's an astounding phenomenon and we'd like to remind people they're not at all dangerous, please don't be afraid and please let us know when you see them."
He added that the crab sightings suggest the sea is healthy and full of life.
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