This is another post about two topics I discuss a lot, viz., "infrastructure" and "why Congo is screwed". If those topics don't interest you, move on.
So Congo touches the Atlantic Ocean, but it doesn't have a proper ocean port. There's Matadi, 150 km up the Congo River. (Nothing goes past Matadi because of the rapids.) But it turns out that the lower stretch of river from Matadi to the ocean is choked by sand bars. The maximum draft? Currently about 6 meters.
That's not much. You can't bring big ocean-going ships into Matadi. Back in colonial times, it was tolerable. But the average ocean vessel today is something like ten times bigger than the average in 1950.
-- You'll notice I said "currently". That's because the lower river can be dredged. In fact, Congo has a couple of big dredges to do the job! But they're not working because of deferred maintenance, lack of spare parts, the usual. A team from the Netherlands is trying to get them going. But even if you dredge like crazy, it only increases the maximum draft to 8 meters -- better, but still not good.
So how do you get goods into Matadi? Two ways.
One, you ship it in a smaller freighter. This happens. Not all the world's freight traffic is carried in immense, 100,000 ton vessels. A fair amount of Congo's imports, especially from Europe, come in smaller ships. But they're more expensive, and you can't easily get them for long-hauls (i.e., to and from China).
Two, you ship it to the nearest deep-water port that can handle large freighters. In this case, that's Pointe Noire, 250 km northwest of Matadi, in the country of Congo-Brazzaville (aka The Other Congo). At Pointe Noire it gets offloaded into one of several smaller ships that run a shuttle service back and forth, along the coast and up the lower Congo river to Matadi.
There are a couple of additional wrinkles. One is that Matadi is a horrible, horrible port. It's overcrowded, most of the equipment doesn't work, and it's afflicted by broad, profound and relentless corruption. It's rated as one of the most expensive ports in the world, while at the same time being one of the slowest.
Another is that the Matadi-Kinshasa rail line is in terrible shape. It's run by a state-owned company, so it's slow, dilapidated, and corrupt. Normally it's much cheaper to move stuff by rail than by road, but the Matadi-Kinshasa line is so bad that 80 to 90 percent of stuff coming in from Matadi uses the road instead.
So, to summarize, most imports to Kinshasa go to Pointe Noire first; get unloaded and reloaded into a much smaller ship; go to the horrible port of Matadi and get unloaded again; and then travel the last 300 km by road.
Okay, this is pretty bad. Are there any solutions on hand?
Well... maybe. With help from -- can you guess? -- China! -- the government of The Other Congo is building an excellent new road from Pointe Noire inland to its capital, Brazzaville. Brazzaville, you may recall, sits right across the Congo River from Kinshasa. Once that road is finished (sometime next year), it will be possible to skip Matadi altogether. Big ships can unload at Pointe Noire, then stuff can come by road to Brazzaville, then cross the river to Kinshasa. The last leg will need a container ferry (there's no bridge), but that's surely doable.
It'll still be pretty Rube Goldberg for the country's most important transport link. But nothing comes easy in Congo. Baby steps.