What is the primary hydrodynamic purpose of the swordfish evolving an effectively smooth, scale-free exterior?

Answer

To minimize surface irregularities, allowing for a more laminar flow of water over the body and reducing drag

The development of this smooth skin is intrinsically linked to speed; prominent external structures like scales create drag, so burying them helps achieve efficient, laminar water flow necessary for bursts of acceleration.

What is the primary hydrodynamic purpose of the swordfish evolving an effectively smooth, scale-free exterior?
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