WAM, aka Wet And Messy or Sploshing, is a kink where the subject gets very dirty (or completely covered) in one or more non-bodily substance(s). More exactly, "Wet" refers to water coverage only (also known as Wetlook), whereas "Messy" refers to any other substances. Subjects may be clothed or nude; specific acts may range anywhere from G-rated (e.g. Nickelodeon slime, game shows, playing in the mud, pieing from classic slapstick & cartoons) to X-rated (e.g. sex in a mudpit, erotic foodplay, BDSM-style humiliation & submission, kinky pseudo-TF).
Essentially any non-bodily substance can qualify, but common substances and overlapping themes include: