At least in the Athenian Navy the rowers were free men. Men of the lower classes who couldn’t afford the hoplite panoply but free men. Very well trained, expert towers who could maneuver the Athenian ships like human powered torpedoes, as the Persians discovered.
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The Spartans took a big chunk of cash from the Persians and used it to build a rival navy, then hired the rowers at a much higher rate than the Athenians could pay. Ended the Peloponnesian War in a trice. They should have had a Reserve Clause.