In Chiapa de Corzo, several companies offer boat trips down the canyon, all for around the same price. The first office you reach is Turística de Grijalva (961 600 6402), on the west side of the plaza. Or you can head straight south down the street to the embarcadero, where other companies operate. During Mexican vacation times, boats fill with the requisite ten people almost immediately, and it doesn’t matter where you buy your ticket. In slower times, it’s best to show up early and go from company to company to see which boat is closest to full. Tours last a couple of hours.