Mudlarking

 Mudlarking -The act of searching the tidal banks(foreshore)of a river,most famously the river Thames in London for historically significant,lost or discarded objects originating in the 18th and 19th centuries as a necessity for the poor,it has evolved into a popular hobby for finding items like Roman pottery, Victorian clay pipes ,and medieval coins.

        A mudlarker is someone who scavengers the banks and shores of rivers for items of value.