Just north of the Pranburi River is an extensive natural mangrove forest. A 1km-long boardwalk with interpretive signs, some in English, lets you explore it from the perspective of a mud-dweller, while an observation tower gives you a bird's-eye view. At high tide fisherfolk will take visitors on 40-minute boat trips (500B) along the river and small canals.
You'll see hundreds of crabs, and usually a fair number of birds, mudskippers and water monitors. In some areas you'll hear snapping shrimp. There's quite a bit of variety within this forest – the ecosystem is different enough from the young, replanted mangrove across the river at Sirinart Rajini Mangrove Ecosystem Learning Center that nature lovers will appreciate visiting both.
It's a 14km drive from Pak Nam Pran via Rte 1019, passing very near Hat Sai Noi on the way. A more direct route half this length is shown on many maps, but it's not passable any more.