As of Jun 19, 2026, 8:54 PM, in season now. Earth Exhibit tracks the live conditions and flags it the moment it is on.
Golfo Dulce is one of the very few places on Earth where the sea glows with bioluminescence year-round rather than in a brief seasonal bloom.
The gulf is a deep tropical fjord on Costa Rica's southern Pacific coast, sheltered from the open ocean by a shallow 60 m sill and plunging past 200 m in its inner basin — the only anoxic basin on the Pacific coast of the Western Hemisphere, and one of just four tropical anoxic systems known worldwide.
That unusual, stratified, sheltered structure keeps bioluminescent dinoflagellates concentrated in the warm surface layer all year, so the glow is effectively permanent.
On a dark night any disturbance — a paddle stroke, a fish, a swimmer's hand, the wake of a boat — sets off a cold blue-green flash as the plankton fire their luciferin reaction in a fraction of a second.
The light is always there; what changes night to night is whether the sky is dark and the water calm.
Guided night-kayak and boat tours from Puerto Jiménez and Golfito take visitors into the mangrove estuaries and open gulf to watch their own wake bloom with light, sometimes alongside dolphins trailing glowing streaks.
Where to see it
A taste of where to see it. The full map, exact coordinates and the best timing for each spot live in the app.
| Viewing spots |
|---|
| Puerto Jiménez Mangrove Estuaries (Golfo Dulce) |
| Playa Cativo / Piedras Blancas National Park (Golfo Dulce) |
| + 2 more spots, with exact coordinates and timing, in the app → |
This is the short version
This page shows a taste. The app has the full list of where to see this, the exact timing, and live conditions for 1,000+ natural phenomena worldwide, so you know the moment one is genuinely worth the trip.