Visibility in the water off Puerto Vallarta, close to the mouths of the rivers is poor in the summer, but away from these locations visibility in the summer is greater than in the dry season. In Puerto Vallarta, the sewage is treated by a British/Dutch company with a "State of the Art" facility. Outside of the City there may be no connection to this and in the rainy season some pollution can happen around the river mouths, but it quickly dissipates in the bay, which is a huge body of water.