Slime reduces drag: fish
 

Skins of fish reduce drag by being covered by a slime layer of complex proteins, polysaccharides, and bacteria.

   
  "Specific organisms can be targeted for specialized purposes. Slick 'no drag' hulls have been sought for centuries. The slickest surface is not a waxed or polished or Teflon surface, contrary to common belief. Using biomimicry, most fish have a clearly articulated slime layer of complex proteins, polysaccharides and bacteria. They are very fast and achieve this speed from the physical/chemical interface of water molecules with the surfaces of the bacteria and components which harbor either thinly affixed water molecules or compounds which have the appropriate hydrophilicity/hydrophobicity balance." (Guritza 2002:1)

  Learn more about this functional adaptation.