Roman concept of naval warfare
was to close with the enemy and board his ships, thus turning a
naval battle into a series of land actions.
This concept lead to what appears to our eyes as a complicated crew structure but it worked for the Romans.
Irrespective of its size the crew consititued a century and just as in the legions this was commanded by a centurion. This included not only the military personnel but also the oarsmen, steersman and clerks. This is evidenced by inscriptions upon which they refer to themselves and are referred to as
milites (soldiers) and not nautae (sailors)