A stream lined body helps an aquatic animal or a bird to move swiftly as it helps in overcoming the opposition while moving through a fluid(viscous drag).
Friction does not depend on the shape of the body exception in stream lined bodies.
Interlocking caused by irregularities of the surfaces in contact affects force of friction. The irregularities interlock into each other which needs a great force to overcome.
Lubricants convert dry friction into wet friction where wet friction is less. Here the lubricant acts as a fluid interface between the surfaces. It fills the irregularities making the surfaces smooth.

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