This long, sandy beach, 14km west of Santa Cruz Huatulco, is backed by a fishing village, and in contrast to Huatulco's other settlements, there's absolutely no resort-type development – just a line of rustic comedores stretching along the beach, serving seafood and fish dishes and simple antojitos (typical Mexican snacks). Usually the waters of the bay are calm, and there is coral with very good snorkeling around the rocks in the bay and at Playa Riscalillo round the corner to the east.
San Agustín is popular with Mexicans on weekends and vacations, but quiet at other times. Some comedores rent out snorkel gear, and most of them can arrange boats to Riscalillo or Playa La India. Many also have hammocks for rent overnight, or tent space; they may let you stay free if you eat with them. El Tronco toward the north end is run by a friendly family and has a tent to rent as well as hammocks.
A 13km dirt road heads south to San Agustín from a crossroads on Hwy 200, 1.7km west of the airport. Buses between Huatulco and Pochutla will drop you at the crossroads, where taxis wait to carry people to San Agustín (M$115, or M$25 per person by colectivo).