Vietnam · South Central Coast
Nha Trang
Best visibility commonly falls outside the heavier rainy and storm season.
Nha Trang is Vietnam's main diving city — easy boat access to a small marine park, mostly soft coral and macro, with mild current. Recovering from years of overfishing; biodiversity is improving but not at regional-best level.
Good season
March–September is best; October–February brings rough seas from the northeast monsoon.
Trip duration
2–3 days as part of a longer Vietnam trip.
Dive style
Boat day-trips; mild current; mostly shallow.
Dive level
Open Water; popular for certifications.
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 ~2097. Losing about 0.4% cover per year — roughly 73 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 · 1.1 °C-week heat dose
What to expect on a dive
Heavily impacted by 2024 thermal stress. Operator-led restoration projects ongoing.
Sources, methodology, and the raw numbers
Raw observed numbers
- Coral cover: 29% (survey Sep 2024, Department of Marine and Coastal Resources Thailand survey)
- Bleached: 14%
- Recent mortality: 5%
- Gulf of Thailand — observed condition reflects the declining regional pattern.
Raw thermal numbers
- NOAA CRW alert level: Watch
- Degree Heating Weeks: 1.1 °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
- Reef Check — Reef Check Foundation
- 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
- 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
- dive-school over-capacity
- warming
- coral disease
2 Green Fins-verified operators known at this location.
What you can do
Hon Mun MPA was Vietnam's first MPA. Koh Tao reefs are heavily loaded with training divers — picking ecology-focused dive schools helps reduce shallow-reef impact.
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.
Pollution & water-quality
What divers should knowHeavy thermal stress + coral mortality
SEVERESince 2024
Severe 2024 bleaching event triggered closure of large parts of Hon Mun MPA to diving for restoration work. Check current status with operators.
What this means for your trip
Hon Mun MPA access has been restricted since 2024 — verify operator permits before booking. Consider Phu Quoc as an alternative.
Dive sites here
1 curatedGear
What to bringWhat divers say
“Don't come to Nha Trang for the diving — come for everything else and dive while you're here.”
