The ancient Mesopotamians did not build boats with weeds. They used reeds, such as the common reed (Phragmites australis), to build boats. These reeds were abundant in the marshlands of southern Mesopotamia and were used to construct boats of various sizes, including small fishing boats and large cargo ships. The reeds were bundled together and tied to a wooden frame to form a sturdy and lightweight hull. The boats were often coated with bitumen, a naturally occurring tar, to make them waterproof.