Jaco Rafting runs descents on the Naranjo and Savegre rivers, in the Quepos and Dominical area, with certified bilingual guides. People who have gone say that on the Naranjo the guides Gregory and Mario explain what to do on entering each class III and IV rapid so you stay in the raft, and that midway there is a break with fresh local fruit; some did it with little experience and wanted to go again. The class II–III Savegre adds swimming pools and waterfalls and a hot lunch at the end; for more adrenaline there is the class IV–V Chorro section, from December to May.
The tours do not leave from Jacó's doorstep: it is an hour's drive to the meeting point, and from there a bus climbs another hour up the mountain through small villages, so plan on a full day. Rates start at $95 per person if you drive yourself and $115 with transport from Jacó; the guides have a name for being safe and friendly, there are photos of the run, and the restaurant at the site serves good food.
Rafting on the rivers near Quepos and Dominical, about an hour from Jacó. Book in advance; certified bilingual guides. The “driving your car” rates are for the meeting point; from Jacó they include transportation. Ask about large family and group specials.