The Babylonians were shrewd businesspeople. Their boats sailed up and down the Tigris and Euphrates rivers and into the Persian Gulf, carrying goods that kept the Babylonian markets busy and the country wealthy.

The Tigris and the Euphrates were highways of Mesopotamian civilization. It was along these rivers that trade took place, and where cities were established. The two rivers bustled with activity as boats sailed up and down them. There were several different kinds of crafts. Many were small boats, while others were larger ships with big square sails that would eventually travel into the Persian Gulf and beyond to trade with distant places.

A cylinder seal impression from a seal found at Tell Billa and likely dating to the late Uruk period. The seal shows a ruler with attendants in what is likely a bitumen-coated reed boat.

Photo from Maritime History Podcast - https://maritimehistorypodcast.com/ep-002-surplus-food-big-buildings-power-hungry-lugals/

The Mesopotamians were very creative in their boat designs. Some of the smaller boats were made of reeds and surrounded with goatskin that had been blown up with air and tied underneath the rafts to make them float better. With these blown-up animal skins the rafts could carry tremendous weights. 

Traveling down either the Tigris or Euphrates was comparatively easy as the traders had the current of the rivers to help move them along. Going upriver was a different story. It was difficult for the simple boats to make the return trip sailing against the current. Therefore, the traders would sometimes get oxen to pull the boats upstream or along the canals. However, more often than not, boats that had floated downriver would be taken apart and their wood sold. Goods shipped upriver were usually carried by donkey caravan.