The Cañon del Sumidero is 32km long. It's situated on the San Cristobal road some fifteen kilometres from Tuxtla.
Note that boats only leave when all seats are taken and hold between 10 and 15 passengers, depending on their size.
The best way to tour this canyon, which is part of a national park, is by taking a motor boat from either Chiapa or Corzo and cruising along the Grijalva River. You can also get a great view from the roadside watchtowers at La Atalaya, Los Chiapas and El Tepehuaje.