The correct answer is - waterway.
The route of water, or as it is more commonly referred to, waterway, is a canal, a river, or another type of route that allows the travel and movement through a body of water, like through a lake, sea, or an ocean.
The waterways and the precise organization of them, are very important because nowadays the water travel and trade are extensively used, and the number of boats and ships is enormous, so in order for collisions or tension situations to be avoided, the waterways have to be carefully managed and respected.