- Tam Giang - Cau Hai lagoon stretches over 68 km across 04 districts: Phong Dien, Quang Dien, Phu Vang, Phu Loc and Huong Tra town with the area of 22,000 hectares.
- Regards to geographical side, the lagoon systems includes 4 lagoons from North to South i.e. Tam Giang lagoon; Sam lagoon; Ha Trung - Thuy Tu lagoon; Cau Hai lagoon.
- Tam Giang lagoons covers an area of 5.200 hectares from O Lau river to Huong river estuary. It joins sea via Thuan An gate.
- Sam lagoon is much smaller with the total area of 1,620 hectares. Unlike Tam Giang lagoon, Sam lagoon is not connected with the sea.
- Ha Trung-Thuy Tu lagoon is long and narrow with the area of 3,600 hectares. Similar to Sam lagoon, it is not connected with the East Sea.
- Cau Hai is the largest lagoon which covering the area of 11.200 hectares. Tu Hien gate connects Cau Hai lagoon and the East Sea.