Sludge Release was created by Hedoro Zeki by combining his Water and Earth chakra natures. It is unknown if it is a kekkei genkai that was first awakened by Hedoro or not. The only way to be sure is if Hedoro's descendents were to possess it, making him the patriarch of his own clan.
Sludge Release shares many properties with Water Release and is generally used the same way. Hedoro claims that the use of it puts little strain on the body, but can leave you tired afterwords. "It feels like throwing up." he claims.