Seeking river-based adventures or encounters for 4th level party

[CroydThoth]

Does anyone know of any good river-based adventures, encounters, background material, (D&D or otherwise) for a party of 4th level adventurers who will be travelling several hundred miles up a well-traveled river?

 

[Starfox]

River into Darkness is a good one, based on the Heart of Darkness novel. It is set in a tribal, tropical river so it might not be appropriate for your needs.

 

[Spellknight]

You might look into a book called Dreadmire.
http://www.dreadmire.com/
It's got a lot of Swamp/River flavor that might give you some ideas.

 

[CroydThoth]

Thanks for the suggestions!