The sights along the eastern stretch past Astata [1] are mostly natural, including mangrove-tufted lagoons, palmy beaches, and breezy viewpoints. What follows is a summary of some ripe possibilities to anticipate along the way. Measure mileage east from Astata or west from the Highway 200 and Trans-Isthmus Highway intersection at the north edge of downtown Salina Cruz.
Moving east from Astata [1], arrive at the Laguna Colorada dirt side road (from Astata east 7 miles/11 km, from Salina Cruz west 41 miles/66 km). The dirt road leads a few miles along the west edge of a glassy, wildlife-rich mangrove lagoon to a beach.
Another several miles along (east 19 miles/31 km, west 29 miles/47 km), another wildlife-rich mangrove lagoon, Laguna Garrapatera, is visible from the highway at Kilometer 348. A wave-washed white sandspit borders the lagoon on the ocean side. The lagoon looks fine for kayaking or rubber rafting, and the beach could be great for camping if you can get to it.
At Kilometer 349, Highway 200 rises to a viewpoint overlooking the idyllic green Río Bamba Valley (east 20 miles/32 km, west 28 miles/45 km). Several miles farther (east 31 miles/50 km, west 17 miles/27 km) arrive at the dirt road turnoff to surfing and seafood-palapa-restaurant Playa Cangrejo (Crab Beach).
Next, pass Morro Mazatán town (east 36 miles/57 km, west 13 miles/21 km). Finally, arrive at the signed dirt side road to Playa Brasil, which has a great oceanfront breeze-blown sand hill on its west end (east 41 miles/65 km, west 8 miles/13 km).
Links:
[1] http://www.moon.com/destinations/oaxaca/pacific-resorts/bahias-de-huatulco/excursions/santiago-astata