From https://en.wikipedia.org/wiki/Swamp_Thing_(song)
"Swamp Thing" is a song by British electronic music group the Grid, released on 23 May 1994 as a single and is included on the Grid's third album, Evolver (1994). It peaked at number three on the UK, Australian, and Danish singles charts and reached the top five in an additional seven countries, including Finland and Norway, where it reached number two. The song was later sampled in "Banjo Thing" by Infernal and "Swamp Thing" by Pegboard Nerds. NME magazine ranked it number 41 in their list of the 50 best songs of 1994.
"Swamp Thing" is almost completely instrumental, consisting mainly of: drums, synthesizer sounds and banjo. The only vocals are Well alright, watch out, Feel alright and I just dig it, sampled from the 1973 reggae song "Papa Do It Sweet" by Lloyd & Patsy. The banjo part was written and performed by Roger Dinsdale – a folk musician who also played the guitar and the mandolin. Dinsdale died in July 2009.