Ô Loan Lagoon covers about 15.7 square kilometers of brackish water, held apart from the South China Sea by a narrow sand dune. A small creek connects the two, allowing seawater to flow in and out with the tides, maintaining the brackish conditions that make the lagoon's ecology distinctive. From above, the dune appears almost impossibly thin — a pale line between the dark lagoon water and the deeper blue of the open sea. The lagoon lies roughly 22 kilometers north of Tuy Hòa. Mangroves line portions of the shore, their roots binding the sediment and creating a complex habitat where the land grades gradually into water. This combination of shelter, salinity gradient, and vegetation draws both permanent resident species and migratory visitors.

The lagoon's reputation rests partly on what can be pulled from it. Blood cockles — *Tegillarca granosa* — thrive in the brackish sediment here and are considered a local delicacy, typically served simply: boiled or steamed, with salt, lime, and chili. Shrimp, crab, and various fish species round out a menu that visitors to the area have been seeking out for generations. The mangrove fringe that makes these harvests possible is also what makes the lagoon worth protecting: the trees buffer the shoreline from storm surge, filter runoff, and support bird populations that use the canopy for nesting and foraging. Vietnam designated Ô Loan a National Scenic Site on September 27, 1996.

A 2015 Vietnamese film called *Tôi thấy hoa vàng trên cỏ xanh* — Yellow Flowers on the Green Grass — was shot partly at and around Ô Loan Lagoon. The film, an adaptation of a novel by Nguyễn Nhật Ánh, follows two brothers growing up in a rural Central Vietnamese landscape. Its images of the lagoon, the flat coastal plains, and the particular quality of light in this part of Vietnam reached audiences across the country and drew visitors who recognized the scenery. For a place that had been quietly beautiful for a long time, the film provided visibility. It also cemented Phú Yên's reputation as "the land of yellow flowers on green grass" — a phrase that has since become a regional identity marker.

Visitors to Ô Loan typically arrive by boat or on foot along the dune path. The lagoon moves slowly: the mangroves filter light into dappled patterns on the water, egrets stand motionless in the shallows, and fishing boats drift with the current rather than against it. The pace is not incidental — it is the point. The lagoon offers the particular quiet of water enclosed by land, sheltered from open-sea swell, with the horizon close enough to see clearly but the restlessness of the ocean held at a distance. In the late afternoon, the sand dune catches the last light while the lagoon water darkens early in the shade of its western shore. The fairy's bird would have found this a sensible place to stop.