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Sea caves of Tonga

Cathedral Cave ('Eua)

  • Max depth30 m
  • CertificationCavern

Diving and fills

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The dive

Through the entrance you come into an amphitheatre about 100 m long and 50 m wide, where daylight falls in through holes in the ceiling. Several tunnels lead off from the main chamber into the rock.

In October 2026 no dive operator is confirmed to take scuba divers here: the only operator on 'Eua that names the cave takes freedivers. The sea around 'Eua is regarded as too dangerous for swimming with whales, and there is no chamber in Tonga. Go only with an operator who knows the cave.
The entrance is at 28 m and tunnels lead off the chamber: stay in the daylight of the main chamber and with your guide, and don't enter the tunnels without cave training and a line.

1 earlier accident or incident has been reported at this cave. Read what happened ↓

Profile and sections

Through the entrance you come into an amphitheatre about 100 m long and 50 m wide, where daylight falls in through holes in the ceiling. Several tunnels lead off from the main chamber into the rock.

The chamber was found in 2001 and is called the largest underwater cave in the South Pacific.

Practical: freedivers visit with Blue Water Retreat on 'Eua when conditions allow. In 2019 divers went there on a whale-watching boat.

Depth and profile
Entrance at 28 m, deepest point 30 m. A chamber of ~100 by 50 m, with tunnels leading off the main chamber.
Configuration
Large, well-lit chamber at depth: recreational gear with a torch, within your no-deco time; not the side tunnels without cave training (estimate).
Who can dive where
  • CaveAt least Cavern
  • Whole caveConfigurations: Backmount / twinset / Sidemount / CCR / Small cylinders / no-mount (speleo sumps)
  • Whole caveGoes down to 30 m (trimix or deco may be needed) · doesn't decide who may dive
Entry or dive feeThrough a dive centre or guide

This is how the planner decides who in your team may dive this cave. Rules your own trip adds (organizer, a mail, the AI) show with your trip.

How to get there

Off the north coast of 'Eua, by boat only. A dive operator taking scuba divers here now is not confirmed (see the warning).

Plan your route ↗

Around Cathedral Cave ('Eua)

FillsNo fill station known nearby

News

All (1)

Accidents and incidents

What happened at this cave before, with the sources. No names are given; read it as a lesson for your own planning.

  • On 11 August 2019 a German diver (40) disappeared after a dive in the cave from a whale-watching boat. According to the guide she had left the group and ascended earlier; her weightbelt and later a fin were found on the chamber floor. The search was called off in worsening weather and what happened remains unexplained.

Access and rules change: check what applies locally right before your trip. Source: GDELT Project and the news feeds of diving magazines. Search for more news ↗ Searched automatically, last on 5 Nov 2026.

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Sources, sharing and disclaimer

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Certification requirements, configurations and trimix depths are estimates for planning. Always check them locally and dive within your training. Compiled from web research (Oct 2026): the Tonga Pocket Guide (caves, dive sites and dive operators, updated June–July 2026), the PADI blog (2015), Divernet (2019) on the diver missing in Cathedral Cave, the Freediving Family brochure (2021), Smartraveller and the UK travel advice on Tonga, and Healthpoint on the chamber in Auckland. The dive operators' own websites could not be opened. The pins of Mariner's Cave, Swallows Cave and Shark's Tooth come from the vavau.to diving and snorkelling guide; the other caves have no pin. These are guided boat dives into sea caves and caverns; certification and configurations are estimates.