navigable body of water, including but not limited to rivers, lakes, seas, oceans, and canals

A waterway is any body of water that can be used for transportation by people in boats. These include rivers, lakes, oceans, and canals.

A floating market on one of Thailand's waterways

They must be wide and deep enough for the boats, and either have no waterfalls and rapids, or have ways for boats to get around them, such as locks.