mudlark

Short definition from Wiktionary

Noun

1. 1
   A pig; pork.
2. 2
   One who scavenges in river or harbor mud for items of value, especially in London.
3. 3
   A child who plays in the mud; a child that spends most of its time in the streets, a street urchin.
4. 4
   A soldier of the Royal Engineers.
5. 5
   Any of various birds that are found in muddy places or build their nests with mud, especially Anthus petrosus and Alauda arvensis.
6. 6
   The Grallina cyanoleuca that builds its nest with mud into a bowl-like shape.
7. 7
   A racehorse that performs well on muddy or wet tracks.

Verb

1. 1
   To scavenge in river or harbor mud for items of value.