Greek ships were about 115 feet long. That's about the same size as three school buses lined up in a row.
Some ships were designed to carry cargo. Others were designed as weapons. The Greeks added a layer of brass to the tip of their warships to make their ships work effectively as a battering ram when needed. Greek ships, whatever their purpose, were powered by sails and oarsmen. They were built to turn briskly and move rapidly through the waters of the Mediterranean Sea.
Before ships left harbor, Greek sailors prayed to the sea god Poseidon to keep them safe.
The Greeks used their ships to trade with other Greek city-states, as well as other civilizations around the Mediterranean. In times of war, their specially designed ships, along with well trained oarsmen and strong sails, helped them to defeat their enemies in sea battles. Athens, by far, had the best navy of all of the ancient Greek city-states. Their ability to fight well at sea was critical to their victory in their war with Persian.