A varying number of marines, usually 10–20, were carried aboard for boarding actions. At the Battle of Salamis, each Athenian ship was recorded to have 14 hoplites and 4 archers (usually Scythian mercenaries) on board, but Herodotus narrates that the Chiots had 40 hoplites on board at Lade and that the Persian ships carried a similar number. This reflects the different practices between the Athenians and other, less professional navies. Whereas the Athenians relied on speed and maneuverability, where their highly trained crews had the advantage, other states favored boarding, in a situation that closely mirrored the one that developed during the First Punic War. Grappling hooks would be used both as a weapon and for towing damaged ships (ally or enemy) back to shore. When the triremes were alongside each other, marines would either spear the enemy or jump across and cut the enemy down with their swords. As the presence of too many heavily armed hoplites on deck tended to destabilize the ship, the epibatai were normally seated, only rising to carry out any boarding action. The hoplites belonged to the middle social classes, so that they came immediately next to the trierarch in status aboard the ship.
Source: Wikipedia
