Tens of thousands of giant jellyfish are swarming off one of Britain's most popular stretch of coastline this Bank Holiday.
Record numbers of the 5ft long monsters - which weigh five stone each - were spotted off the Dorset coast. The unprecedented invasion of barrel jellyfish may due to over fishing which leaves fewer predators to eat them when they are young and smaller.
The jellyfish, which are more than three feet wide, may also have overwintered in the depths of UK waters.
Tens of thousands of giant jellyfish are swarming off one of Britain's most popular stretch of coastline over the Bank Holiday
Conservationist Steve Trewhella spotted the swarm from his dive boat off the coast of Kimmeridge in Dorset and even swam with them
Their sting is not considered dangerous to humans but is similar to that of a nettle and can cause a rash.
Conservationist Steve Trewhella spotted the swarm from his dive boat off the coast of Kimmeridge in Dorset.
The unprecedented invasion of barrel jellyfish may due to over fishing which leaves fewer predators to eat them when they are young and smaller
The jellyfish, which are more than three feet wide, may also have overwintered in the depths of UK waters
Their sting is not considered dangerous to humans but is similar to that of a nettle and can cause a rash
Steve, 51, who has been taking underwater photographs for more than 30 years, said he had never seen so many.
BARREL JELLYFISH: THE HARMLESS GIANT
They look like something from a horror film, but barrel jellyfish are the 'basking shark' of their species - enormous but harmless, feeding only on miniscule prey.
Often they are spotted from boats in the deeper waters of the English Channel, the Irish Sea and off the Outer Hebrides.
But it is rare for them to swim closer to the coast or inland, which is why recent sightings have made headlines. And when the seas warm up in summer and autumn they breed at a phenomenal rate, creating huge swarms.
Beneath the dustbin lid-shaped bell are hundreds of tiny mouths ('pores'), each surrounded by tiny stinging tentacles to catch plankton.
The stings, however, are not strong enough to harm humans.
Source: Marine Conservation Society
The diver, from Wareham, Dorset, said: 'Finn had never seen one and I hoped we might be able to spot a couple and he would be able to get into the water with one. We never expected to stumble across more than we knew what to do with.
'They were wonderful and such magnificent animals, and you just can't help but be impressed when you see a four foot long jellyfish by your side.'We saw one and then every couple of seconds another, and another and another. We last got such a glut of them in the 1980s but it was nothing like what I saw this year. They were just everywhere. I've never seen anything like it.'
The barrel jellyfish – the largest species found in south-west England – is not rare in the UK, but are more often seen washed up on beaches and it is unusual to see more than one bobbing along in the water.
Steve, who was also with wife Julie, said he first spotted a single one and was disappointed when it disappeared before he got into the water. But he then went in and found himself surrounded by more than a hundred.
He added: 'If there was a 100 around us, then you would only have to move along a bit and there would be another 100 and another hundred. 'I wouldn't like to guess how many were there - tens of thousands of them at least.
'We don't really know why and I would be speculating but they are plankton feeding jellyfish and they just go around hoover it up, so maybe it is a very good year for plankton. 'Also I've been travelling all over the UK coastline this year and found these jellyfish washed up on many beaches over the winter, suggesting they are overwintering here.'
The barrel jellyfish - Rhizostoma pulmo - is found in the northeast Atlantic and Mediterranean and is the biggest species to be found in the UK. Whilst it can sting, it is not dangerous to humans and only eats plankton.
Experts say their stings are not powerful enough to do any serious harm, but warn swimmers that it is best not to touch them.
The barrel jellyfish – the largest species found in south-west England – is not rare in the UK, but are more often seen washed up on beaches and it is unusual to see more than one bobbing along in the water
Experts say the jellyfish's stings are not powerful enough to do any serious harm, but warn swimmers that it is best not to touch them
