The open boats featured in Tony Stroud's 1950s picture below are "double ended" whelk boats.
Above: The Sheringham Crabbers of the Whitstable whelkers - moored at the harbour's "Dead Man's Corner". Photo kindly supplied by Tony Stroud.
The true reference to this type of boat is 'Sheringham Crabber' and it originated in East Anglia. The boats migrated to Whitstable from Sheringham and Cromer at the end of the 1800s and they have always occupied the South East corner of the harbour (affectionately known as Dead Man's corner).
Many local family names originate from those early migrant fishermen. They came to live in Whitstable and fish for whelks on the Kentish Flats. They brought another method of fishing with them in the form of 'The Whelk Pot'.
My dad's vessel, the "Welcome Messenger", was a Sheringham Crabber and it was one of the original boats to come from East Anglia. Of course, they were originally built for sail and oar. Tony's picture shows younger versions - built locally but based on those early ancestors.
One original whelker was Derek West and he carried on "whelking" until recently I believe. I understand that his boat the Floreat (F91) is now outside at the museum.
The story of the the migration of families from east Anglia is picked up by Ian Johnson in his article "Sheringham and the Johnson Family". Ian's family were part of the migration in 1901.