Professional lobster catcher Graham Barker said he watched a beast similar to those described in recent Herald and Gazette reports when he was out on the water last June.
The animal was walking along the shoreline and he initially thought it was a big dog.
Mr Barker, of Beltring Road, said, "We were at Beachy Head at about 4.30am one day last June and we saw what we thought was a large dog running along the shore. We went nearer to have a look and realised it was a big cat. It was sat there on a black rock for about 15 minutes — 200lbs of jet black cat with a white mark on the right hand side of his cheek.
"Fifty feet away was close enough."
Three weeks later they were told somebody who had later been in a boat by the shoreline had found large paw prints at low tide.
Mr Barker said, "I couldn't believe it.
"He exists, he is up there.
"Two of us were in the boat. We took cameras up with us for the next six weeks but didn't see him again."
He added he has heard at least one other fisherman say they have seen the big cat.
Two separate sightings have been reported to the Herald this month.
Two motorists reported their sightings in Arlington to Kent Big Cat Research and John Hescott from Langney spotted a similar animal in a play area in Faversham Road, just 100 yards from where he was standing.
Sussex Police confirmed they received a report of a possible sighting of a big cat in the Langney area of Eastbourne on Monday January 8, around 7pm.
Experts believe big cats could have survived and reproduced in the wild since being freed from life as a pet in the 1970s.
Regulations about their keep meant many did not want them anymore.
Neil Arnold, of Kent Big Cat Research, put forward another theory.
He said, "The Romans brought thousands of cats over with them and in the 1800s and 1900s big cats were often part of travelling menageries, and more recently leopards and pumas were kept as pets during the 1960s and 1970s."
If sighted, a big cat should not be approached.
claire.watson@trbeckett.co.uk