The Marismas Nacionales–San Blas mangroves occupy an area of in coastal
Nayarit and
Sinaloa states. The Marismas Nacionales is an interconnected complex of lagoons and wetlands on the alluvial plain formed by the
Acaponeta,
San Pedro Mezquital, and
Grande de Santiago rivers. Beach ridges separate the wetlands from the sea. The central
Agua Brava Lagoon and northern
Teacapán Lagoon are the principal lagoons. The San Blas mangroves are the southernmost in the complex, located south of the Grande de Santiago river mouth. Other mangrove areas north of the Marismas Nacionales complex include the
Presidio River delta, the
Baluarte River delta, and the Urías estuary south of
Mazatlan. ==Flora==