supernatant (adj.) Look up supernatant at Dictionary.com
"floating on the surface," 1660s, from Latin supernatantem (nominative supernatans), present participle of supernatare "to swim above," from super "above, over" (see super-) + natare "to swim," frequentative of nare "to swim" (from PIE root *sna- "to swim"). Related: Supernatation (1620s).