mudlarker means one who mudlarks. Lexicurio rates it Sui generis — a strength score of 87 out of 100.
Why “mudlarker” is a great word
MUDLARKER — [Noun] A person who scavenges in river mud, especially the tidal Thames, for items of value or historical interest. From mudlark (a term for a person who scavenges in mud, from mud + lark (in the sense of engaging in a playful or spontaneous activity)) + the agent noun suffix -er. First attested in 1818. Unlike a scavenger, whose pursuit is general and grim, or an archaeologist, whose work is systematic and scientific, a mudlarker is an amateur archivist of the silt, a reader of the tidal archive. It is the patient stoop over glinting Tudor glass, the careful rinse of a mud-cloaked Georgian pipe stem, the quiet triumph of a smoothed Roman coin in the palm—a private communion with all a city has casually lost and a river has faithfully kept.
Etymology
From mudlark + -er.