Most people who come to San Blas come for the beaches. The most important are Playas Hermosa and El Borrego, the town’s main beaches, two adjoining strands of silvery gray sand that extend for about a mile and a half from the foot of Calle Heroicó Batallon de San Blas. Nearby Las Islitas on Matanchen Bay has long, gentle waves ideal for extended surfing. Playa del Rey and the Huichol sacred island lie across an estuary from the customs house. This is not really an island, but the tip of a peninsula, and the southern end of the Marisma Nacional, or National Swamp, which ends just south of Mazatlan. The main tourist attraction is the La Tovara Springs trip, an approximate three-hour guided boat trip through the estuary and mangrove swamps to a natural pool at La Tovara Spring, where you can swim, possibly in the company of an allegedly tame crocodile.

Overlooking the town on a jungle-clad hill is the old hillside ‘fort,’ or Contaduria, which was built in 1770 as accounting offices for the town's extensive sea trade with the Orient. On its front are stone carvings of the kings of Spain. Down a slope from the Contaduria are the ruins of the Church of Our Lady of the Rosary, started in 1769. The ruins once contained the bronze bells which reportedly inspired Henry Wadsworth Longfellow's poem, ‘The Bells of San Blas,’ although Longfellow never did visit the town.
The Las Palmas Crocodile refuge is another local attraction where quantities of these large reptiles can be seen in their natural environment. The refuge carries out a crocodile breeding program organized by the local community with government help in order to preserve and protect the endangered American crocodile. The town is famous for its abundance of migratory birds in the surrounding estuaries and lowland palm forests, attracting bird-watchers from around the world. The town is also gateway, along with the nearby village of Matanchen, to the La Tovara national park, a massive mangrove forest and federally-protected nature preserve that can only be accessed by the small boats that ply the single canal flowing through its midst. San Blas boasts countless beaches. Many believe the town's notorious population of sand-flies have kept them safe from touristic development. San Blas sits like a sliver of land in between two estuaries. These two estuaries, the Pozo and El Rey, are the main entries into a vast wetlands system. The many rivers that flow through the mangrove forests serve as the breeding grounds for fish. The wetlands also serve to buffer the land from storms and prevent erosion.
Recent incursions by shrimp farms have threatened the balance in this very fecund ecosystem. A local environmental movement has helped to mitigate the loss of substantial mangroves and diversion of waters. While claims that San Blas has suffered a loss of fish and wildlife due to development may be true, this area remains abundant in birds, insects and reptiles.