How to build a cargo port? (Cities: Skylines)

Vadser
There are arrows that indicate the route of the cargo ship, it needs to be made available. I put it myself by the "typing" method.

I immediately began to play on my map, I have routes in all directions and you can build anywhere with an exit from the sea.

Prometeo
can be more detailed, I just can't figure out where these arrows are

zaharbaz
When you set up a cargo port, there is a straight line from it to the sea! It is necessary to make this line green, and then the ship will be able to freely pick up cargo from the port and go to sea!

The sea in the city center or something I don't understand

KOsMILE_UA
route must be straight and water. this is such insanity of developers

KOsMILE_UA
There you go! I have the same! The red dotted line from the city center stretches

since the route can only be direct and it cannot (unfortunately) be laid as a road, not everywhere it can be set
an example:

It is not necessary to connect the port to the end of the water route, you can "sideways", the route itself is like a road, you can make branches, for example, you can create four sea links with the outside world, and then combine them into one line on your map, which will pass wherever you might potentially want to build a port.

If you deepen the bottom upstream, slightly widen the banks (if the channel is very narrow), then you can put the port much further from the place where it could have been originally. The "high bank" problem may arise. Then lowering the height of the coastline helps. This is how I raised the port much higher, closer to my industrial area. Theoretically, the port can be raised to the very top, but then, apparently, the whole channel will have to be straightened)

How to build a port if there are no water routes on the map (two rivers)? Maybe there are mods that will add these routes or disable binding to such routes? I want to build a monument, but there is no way without a port. And I don't want to play with another card.