The Sealed Waters

Inside the karst of Ha Long are lakes of sea water sealed when the ocean last rose, cut off from every current for thousands of years. Each has developed its own salinity, its own oxygen at depth, its own descendants of open-sea species.

The limestone here stands in two states at once — drowned in the bay, standing above the fields inland — and the same process made both: fresh water dissolving the rock from within, the sea cutting its notch from without. The film follows that shaping, and then goes inside it. The enclosed lakes are its centre. Everything around them is their frame: the rock that carved them, the sea-level history that closed them, the inhabited surface above, and the pressures that reach even a world with no exchange.

Sealed for millennia and still changing, the lakes are the sharpest place on this coast to watch life meet a world that will not hold still. The film ends inland at dusk, on the freshwater karst of Tam Coc — the same geology in another register, worked and lived in.

The other chapters

The Long Threshold — the lagoons of Hue.
The Great Reversal — the flood-pulse of the Tonle Sap.