What is a marsh?

The big shock for all the Maltese people who, like me, were Enid Blyton junkies when they were children, was that at one point they realised there is no Rubadub mansion, no wooden panelling behind which there is a secret passage, no scones at teatime (What are scones anyway?), no autumn leaves, no boarding schools, no policeman saying "Clear Orf!", no mist and marshes, no friends with an insurmountable urge to create a secret society with a secret password.