James Blish
From The Best of James Blish
Surface Tension
(1952)
Synopsis: A science crew whose job it is to seed planets
with colonies of humans crash lands on a mostly water planet, and even though
they will die there, they seed the planet with microscopic water breathing
humans so small that a grain of sand is like a manhole cover. The story is
about their survival, their conquering of their environment and even going out
into what they think is “space.