While the swimmer's movements may be smooth and fluid, people have neither fins to stay afloat or generate speed, nor gills to deal with going under.
⇑ Translate the sentence above by Google ⇑
Related: fluid
Prev: OK, now we also want some drawing pens, ink and correction fluid, and some drawing paper.
Next: The lungs of a fetus secrete a liquid that mixes with its mother's amniotic fluid.