I kayaked there around 1996-97. I lived with a family in San Gil. Nice mellow town. River runs right through it. Back then, there was a small boating community, I was the only American there at the time, and I think only the second American that had come to boat, after a guy named John from Idaho. I did get to paddle some fun stuff, but other plans I had were spoiled by the guerrillas in the area, we were told it was too dangerous to go into certain areas. Many planned river descents were cancelled because of this. Rio Chicamocha was good big water class III in a canyon bigger than the Grand Canyon. There is quite a bit of paddling to do around there, it's been a while for me so I can't really remember. I think things have stabled out quite a bit, not sure what the paddle scene is like there now, I bet it has gotten better, when I was there there was nothing but exploration, nobody had really been doing anything.
Great place to go though, loved the people and the town.