Dean's Blue Hole — Ari Atoll

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Hotels, dive operators, gear, and how to get here are on the Ari Atoll location page.

Overview

Descend into Dean's Blue Hole, the world's second deepest known blue hole, plunging 202 meters into the earth near Clarence Town, Long Island. Famous for its dramatic geological formations and as a premier freediving destination, the hole offers exceptional visibility into its profound depths. The rim hosts unique marine life, while the interior is a stark, captivating abyss. An unparalleled site for technical divers and freedivers seeking extreme depths and geological wonders.

Briefing note

Access to Dean's Blue Hole is generally unrestricted for recreational and freediving. Be aware of freediving competitions which may limit access temporarily. Technical diving here requires significant experience and appropriate training/equipment due to the extreme depth.

What you'll see

3 species curated

Caribbean Reef Shark
seasonal
Peak: May · Jun · Jul · Aug · Sep · Oct
Green Sea Turtle
year-round
Schooling Fish (various)
year-round

Sightings evidence

3 records on file

Caribbean Reef Shark
medium confidence
Last confirmed
Jun 2024
Recent records
15 within 25 km
Cluster months
May, Jun, Jul, Aug, Sep, Oct
Green Sea Turtle
medium confidence
Last confirmed
Jun 2024
Recent records
20 within 25 km
Schooling Fish (various)
low confidence
Last confirmed
Jun 2024
Recent records
25 within 25 km

Sources & methodology

How we summarise this

We aggregate confirmed occurrence records from GBIF and OBIS within a fixed radius of each dive site. Occurrence records confirm presence and reveal seasonality clustering, but they DO NOT measure per-dive probability — there is no eligible-effort denominator. We deliberately do not publish a numeric '% chance of sighting' from this data.

Sources

Global Biodiversity Information Facility — GBIF Secretariat
Ocean Biodiversity Information System — IOC-UNESCO
OBIS-SEAMAP — Duke University Marine Geospatial Ecology Lab / OBIS
iNaturalist — California Academy of Sciences & National Geographic Society
IUCN Red List of Threatened Species — International Union for Conservation of Nature
WoRMS — World Register of Marine Species — Flanders Marine Institute (VLIZ)
FishBase — FishBase Consortium
Atlas of Living Australia — CSIRO / GBIF Australia
REEF Volunteer Fish Survey — Reef Environmental Education Foundation

Conditions

Month	Water	Visibility	Current
Jan	25–27 °C	15–30 m	none
Feb	25–27 °C	15–30 m	none
Mar	25–27 °C	15–30 m	none
Apr	25–27 °C	15–30 m	none
May	27–29 °C	15–30 m	none
Jun	27–29 °C	15–30 m	none
Jul	27–29 °C	15–30 m	none
Aug	27–29 °C	15–30 m	none
Sep	26–28 °C	15–30 m	none
Oct	26–28 °C	15–30 m	none
Nov	26–28 °C	15–30 m	none
Dec	26–28 °C	15–30 m	none

Season calendar

Divable year-round — no distinct peak season

Next step

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