As of Jun 19, 2026, 8:54 PM, peak season now, through ~July 20. Earth Exhibit tracks the live conditions and flags it the moment it is on.
Small bioluminescent crustaceans, commonly called sea fireflies or umi-hotaru (primarily Vargula hilgendorfii), form visible glowing swarms in sheltered coastal waters of Tokyo Bay and adjacent Chiba shorelines.
Visibility depends strongly on water temperature, tides, and local light pollution, and the phenomenon is most reliable on warm, calm nights in early summer.
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 |
|---|
| Umihotaru Observation Deck (Tokyo Bay Aqua-Line) |
| Magarigawa Estuary Shoreline (Kisarazu) |
| + 1 more spot, 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.