We had a great time doing this. We paired it with the zip lining.
The road to go there was reallllllllllly bumpy and muddy, which was fun in itself. We drove past the orange groves, and mangroves, awsome!
Think we were on the river for 30 mins or so. The guide will attach all the tubes together in one large "snake". We had 10 tubes attached on ours. The guide has the lead tube at the front, so if you don't was to worry about your tube Getting hit by overhead branches, sit as close to te guide as possible (middle is good too, the poor end guy hit a lot of vines/trees) The river was "dark" but felt and smelt clean. The jungle was beautiful. Water was refreshing. No bugs when we went (we were there in dec 2014, and it was hot!!)
The only huge con for me was our guide was really loud, and wouldn't stop talking... I wanted to sit back and enjoy, and he kept talking the whole ride (and not historical things either)