D&D General Setting a campaign on a river

[GuyBoy]

Throat leeches appeared in an early White Dwarf. Basically choked you if you drank river water they were in. Another cheerful little denizen.

 

[Yora]

Great suggestion. Water parasites are great fun, if you don't have them.

A river system can basically be thought of as being fractal. For game purposes, we don't need to worry about terrain elevation when making a waterway map, and we also don't need to be very specific about the depth and width of rivers and the amount of water that is flowing through any given point. And in an explorer campaign, not knowing how far the river goes is part of the whole premise.
So we basically can just keep adding more branches as the players reach the end of any branch they are currently on. And if it starts to look too unrealistic on the map, you can always tell the players that this is the end of this branch, and go back downstream for 50 miles and start exploring another branch.

One neat little side effect is that you can have extremely polluted side branches as an environment hazards, but as more and more branches merge together, it becomes so diluted that it's no longer a threat.

 

[Rabulias]

Far from your premise, but somewhat related, is Philip Jose Farmer's Riverworld series (Riverworld - Wikipedia).

 

[Rabulias]

Throat leeches appeared in an early White Dwarf. Basically choked you if you drank river water they were in. Another cheerful little denizen.

Like a number of White Dwarf monsters, they showed up in the AD&D 1st edition Fiend Folio, too.

 

[Yora]

Some more ideas:

• A giant ancient bridge spanning the river at a wide point. It's so big that is has a network of tunnels running under the road, which have become home to all kinds of things. That might by praying on boats passing underneath.
• Giant spider monsters have made huge nets that span between trees on both sides of the river to hunt birds. And could be a problem to boats getting stuck as well, or larger ships getting swarmed with spiders as they try to push through.
• Old port on the riverbank that has mostly sunken into the rising river.
• Old port on the riverbank that sits now very high above the lowered river.
• An abandoned merchant ship that has been overgrown with vines, but can be plugged up to float downriver to a port.
• A wrecked merchant ship that needs someone to help them rescue their passengers and as much of the cargo as possible.
• A ship floats down the river without a crew and in perfect shape.
• Sailors float down the river without a ship. And they are dead.
• River maidens. Flesh eating river maidens.

 

[GuyBoy]

Were-otters (of the giant Amazonian variety), probably good aligned and helpful.
An old, but still working, watermill; it can be a lair of some type, with the prospect of a swashbuckling fight on the turning slats of the wheel.

 

[Yora]

I love otters and seals (and weasels). There's actually seals in the Caspian Sea and Lake Baikal, however they might have gotten there.
And it never hurts to have an ancient dugong oracle.

 

[BookTenTiger]

What I like about the idea is that it contains within itself a great narrative cycle. As a player I could expect my character to go up the river, find adventure, go back down the river. Then go further up the river, find adventure, go back down the river. I like too how the trip back down the river will be faster - after delving a dungeon you want to get home fast!

One fun thing you could have is ways to upgrade the group's boat. They could start with a raft, then over time invest in larger boats, a crew, some weapons, magic sails, etc.

 

[Yora]

Or establish a trade post as your own supply depot, where merchants come to bring you new supplies and take the treasures you recovered.

I am taking influences from base-building survival games for this.

 

[Yora]

I want to go really fantastical with my campaign, so

"Why paddle, when you can ride?"

My initial idea was to do mostly ruin scavenging. But the more I think of it, I feel having a strong trade element would also fit in really well. Those river merchants keep grabbing my attention as a major component of the campaign.
And with the explorers being treasure hunters and scavengers, they are also in the business of selling stuff that is scarce and fetches a high price. So I am thinking players having a side gig going as traders could also be a lot of fun. In addition to trade posts, there could also be various mining towns and the like further up the river. If there's still room on their boats on the return trip, they could load up on a valuable resource and sell it in one of the larger ports.

Which I guess means I have to look into Ultraviolet Grasslands now.