The rivers are short and shallow in the Pacific vertient, larger and deeper, such as the Polochic which drains in Lake Izabal, Río Dulce, Motagua and Sarstún that forms the boundary with Belize in the Caribbean and the Gulf of Mexico vertient (Usumacinta, which forms the boundary between Chiapas, Mexico and Petén and its tributaries such as La Pasión and San Pedro.