The jellyfish were strewn across East Beach in Littlehampton on Wednesday (January 6) in their hundreds, among the seaweed washed up near the pier.
Their unseasonable appearance was caused by recent storms and mild temperatures, according to an officer from the Sussex Wildlife Trust.
Although they varied in size, one of the larger specimens, a barrel jellyfish (pictured above), came to around fifty centimetres in diameter.
Olle Åkesson, marine officer at the Sussex Wildlife Trust said: “It’s a little more unusual to see them this late in the season. They’ve probably been carried in from farther offshore, probably by the recent storms.
“You’ll normally see much fewer this time of year, and I wouldn’t have really expected to see this many of them.”
He said the jellyfish get ‘kicked up’ from the seabed in the storms and the warmer than usual water temperature means there are more plankton and nutrients for them to eat.
However, despite their size, Mr Akesson said the jellyfish were ‘harmless’.
In August the Marine Conservation Society reported record numbers of barrel jellyfish sightings for a second consecutive year.
One dog walker said: “You see everything here at low tide.
“Half a boat was washed up the other day, upside down with the rudders showing. Shoes are washed up, cardigans too – and crabs and sea coal.”
Don’t miss out on all the latest breaking news where you live.
Here are four ways you can be sure you’ll be amongst the first to know what’s going on.
1) Make our website your homepage
2) Like our Facebook page
3) Follow us on Twitter
4) Register with us by clicking on ‘sign in’ (top right corner). You can then receive our daily newsletter AND add your point of view to stories that you read here.
And do share with your family and friends - so they don’t miss out!
Always the first with your local news.
Be part of it.