The navies of ancient times were dominated by a warship called the trireme. These fierce ships were fast and furious. Motivated by three ranks of oars pulled by over 150 men they could reach speeds up to 10 knots. The top deck carried a small crew of archers and marines who did the fighting in case of close conflict.
Triremes were of various lengths but averaged about 18 feet wide and about 130 feet long. Their primary weapon was a ram at the front of the bow which was right about at the water line. The primary tactic of attack was to build up momentum by heavy rowing and then smash into an enemy vessel, hopefully avoiding the enemy's ram at the same time.
Built of wood and equipped with sails they had some range, but they were fairly top-heavy and very likely to flip over in a heavy storm. For this reason they were a fair-weather vessel, seldom used during the winter months. Also, fleets tended to hug the coast and to put into shore to camp over night. There was not much cross-sea traffic.
The Athenians tended to build their ships slightly bigger than the Phoenicians (the prime element of the Persian navy). Because of this they had a weight advantage in a collision, but they also were slightly slower and less maneuverable.
Both navies at Salamis comprised of this type of ship. Both had experienced crews. Both had intelligent leadership. But the Greeks had two advantages. First, they were fighting for hearth and home. Second, they had an amazingly astute leader, Themistocles.