Federated States of Micronesia · Chuuk
Chuuk Lagoon
Main wreck-diving season with more settled weather.
Chuuk Lagoon (Truk) holds the largest concentration of WWII shipwrecks on Earth — 60+ Japanese vessels and aircraft sunk in Operation Hailstone in 1944, now coral-encrusted and intact. It's the world's premier recreational wreck destination.
Good season
Year-round; December–April is driest. Water temp is a steady 28–29°C.
Trip duration
7–10 night liveaboard, or land-based at Blue Lagoon Resort.
Dive style
Wreck penetration, often deep (30–40m). Nitrox standard; many divers add rebreathers and technical training.
Dive level
Advanced + wreck specialty for penetration; tech training recommended for deep wrecks.
Reef health
What you’ll actually findSome loss since the 2010s, but the reef still has plenty to dive. Pick depth and shoulder-season carefully.
Coral reef health
How is this calculated?On current trend, no live coral by ~2199. Losing about 0.2% cover per year — roughly 175 years of reef left to see if nothing changes.
Heat stress right now
Mild warmth. Worth watching — no bleaching yet.
NOAA Coral Reef Watch · updated May 2026 · 0 °C-week heat dose
What to expect on a dive
WWII Japanese fleet with extensive coral growth on the wrecks. Lagoon conditions remain stable.
Sources, methodology, and the raw numbers
Raw observed numbers
- Coral cover: 35% (survey Sep 2024, Chuuk Lagoon coral-on-wreck benthic survey)
- Bleached: 8%
- Recent mortality: 2%
- Chuuk lagoon — observed condition reflects the stable regional pattern.
Raw thermal numbers
- NOAA CRW alert level: Watch
- Degree Heating Weeks: 0 °C-wk
- SST anomaly: +0.7 °C
How we summarise this
Observed coral cover, bleaching, and mortality come from named in-situ surveys with a stated date and method — they describe one snapshot of one reef and do not extrapolate to neighbouring sites. Current thermal stress is satellite-derived from NOAA Coral Reef Watch at ~5 km resolution; it indicates risk, not observed coral damage. We deliberately separate observed condition, current thermal stress, and projection — and we never publish a projection without a documented model and uncertainty.
Sources
- International Coral Reef Initiative — ICRI Secretariat
- NOAA Coral Reef Watch — U.S. National Oceanic and Atmospheric Administration
- AIMS Long-Term Monitoring Program — Australian Institute of Marine Science
- Global Coral Reef Monitoring Network — GCRMN / ICRI
- Atlantic and Gulf Rapid Reef Assessment — AGRRA Program / Perry Institute for Marine Science
- NOAA National Coral Reef Monitoring Program — NOAA Coral Reef Conservation Program
- Reef Check — Reef Check Foundation
- NOAA CoastWatch / OceanWatch — NOAA NESDIS / STAR
- Allen Coral Atlas — Arizona State University Center for Global Discovery and Conservation Science
- Great Barrier Reef Marine Park Authority — Australian Government
- Reef Life Survey — Reef Life Survey Foundation
- NASA PO.DAAC — NASA Jet Propulsion Laboratory / Caltech
- Copernicus Marine Service — Mercator Ocean International for the European Union
- NASA Ocean Color (OB.DAAC) — NASA Goddard Space Flight Center / Ocean Biology Processing Group
- Argo float network — International Argo Program / UCSD
- CoralWatch — University of Queensland
- IMOS / AODN — Integrated Marine Observing System / Australian Ocean Data Network
- WRI Reefs at Risk Revisited — World Resources Institute
- Ocean Health Index — OHI partnership (Conservation International + UCSB + NCEAS)
- IPCC Special Report on the Ocean and Cryosphere (SROCC) — Intergovernmental Panel on Climate Change
- GOA-ON — Global Ocean Acidification Observing Network — GOA-ON Secretariat + IOC-UNESCO
- HAEDAT — Harmful Algae Event Database — IOC-UNESCO Intergovernmental Panel on Harmful Algal Blooms
- NCEI Marine Microplastics — NOAA National Centers for Environmental Information
Reef condition changes year to year. If you visit, consider supporting responsible-travel and conservation operators on the ground.
Pressure on this reef
Protection · fishing · what you can doProtected-area status
Multi-use MPAInside a designated MPA that permits regulated fishing and other uses. Worth checking which zones at this location are no-take.
Fishing pressure
Moderate fishing pressureDominant pressures
- industrial fishing on EEZ edges
- warming
1 Green Fins-verified operator known at this location.
What you can do
Chuuk wrecks are legally protected as cultural heritage under Micronesian law. Yap, Chuuk, and FSM mix traditional tenure with national park designations. Chuuk wrecks are legally protected as cultural heritage.
Protection status sourced from Protected Planet / WDPA and refined with Marine Protection Atlas. Fishing pressure proxy is Global Fishing Watch AIS data. See the methodology for what these sources can and can’t prove.
Dive sites here
5 curatedFujikawa Maru
Japanese aircraft transport sunk in Operation Hailstone, February 1944. Lies upright in 36 m with Zero fighter parts in cargo hold #2 — incl…

Shinkoku Maru
Japanese fleet oiler torpedoed during Hailstone. Sits upright at 38 m — bow rises to 12 m. Operating theatre with surgical instruments still…

San Francisco Maru
The Million Dollar Wreck — a Japanese armed cargo ship sunk by USS Essex bombers during Operation Hailstone on 18 February 1944. Sits uprigh…

Heian Maru
Truk Lagoon's largest wreck: a 163 m NYK ocean liner converted into a submarine tender, sunk during Operation Hailstone in February 1944. Sh…

Nippo Maru
Japanese armed water-and-supply transport sunk during Operation Hailstone in February 1944. She sits upright with a list to port, holds pack…
Gear
What to bringSite-specific add-ons
Some dive sites here call for extra gear. Check the individual site page for full context.
- Dive light — Cargo holds and engine room penetration — primary plus backup. · Fujikawa Maru
- Computer — Multi-level deep wreck — Nitrox recommended. · Fujikawa Maru
- Computer — Trimix dives common to maximize bottom time. · Shinkoku Maru
What divers say
“Swimming through the engine room of the Fujikawa Maru is like time-travel with a regulator in your mouth.”