Palau · Micronesia
Rock Islands
Dry-season conditions usually make inter-island boat travel easier.
The Rock Islands in Palau's southern lagoon include the famous Jellyfish Lake — a saltwater pond cut off from the sea where golden jellyfish have evolved with reduced stings, allowing snorkelers to swim among millions of them. Plus countless dive sites among the limestone islands.
Good season
Year-round; November–May is drier. Jellyfish population fluctuates with ENSO cycles.
Trip duration
5–7 nights as part of a Palau trip.
Dive style
Snorkel-only for Jellyfish Lake; scuba on surrounding island walls and channels.
Dive level
All levels for jellyfish snorkel; Advanced for Rock Island dives.
Reef health
What you’ll actually findOne of the few reefs whose live coral has held up over the last decade. Plan with confidence.
Coral reef health
How is this calculated?Heat stress right now
Mild warmth. Worth watching — no bleaching yet.
NOAA Coral Reef Watch · updated May 2026 · 1 °C-week heat dose
What to expect on a dive
Rock Islands marine lakes and outer reefs both remain in strong condition under Palau's national MPA regime.
Sources, methodology, and the raw numbers
Raw observed numbers
- Coral cover: 40% (survey Sep 2024, Local Pacific reef survey)
- Bleached: 6%
- Recent mortality: 2%
- Pacific refugium — observed condition reflects the stable regional pattern.
Raw thermal numbers
- NOAA CRW alert level: Watch
- Degree Heating Weeks: 1 °C-wk
- SST anomaly: +0.4 °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
No-take reserveFully no-take — no fishing of any kind. The strongest protection tier.
Fishing pressure
Low fishing pressureDominant pressures
- dive tourism
- warming
3 Green Fins-verified operators known at this location.
What you can do
Palau National Marine Sanctuary protects 80% of the EEZ as no-take. The Palau Pristine Paradise Pledge is signed on arrival — read it and live it.
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
2 curated
Ulong Channel
A natural cut through the barrier reef west of Ulong Island, often picked as Palau's signature drift. Enter at the channel mouth around 18-2…

Blue Corner
A triangular reef plateau jutting off the northwest tip of Ngemelis Island, where Palau's barrier reef drops sharply into open ocean and cur…
Gear
What to bringSite-specific add-ons
Some dive sites here call for extra gear. Check the individual site page for full context.
- Reef hook — Hook-in at the channel entrance is the standard technique to watch sharks and snappers without finning against the current. · Ulong Channel
- Surface marker buoy — Drift exits the channel into open water — operators require SMB for pickup. · Ulong Channel
What divers say
“Floating in a million pulsing golden jellies in a lake on top of an island — Palau's strangest hour underwater.”