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Hotels, dive operators, gear, and how to get here are on the Riviera Maya Cenotes location page.
Overview
A vertical shaft 17 km south of Tulum that drops past a 30 m hydrogen sulfide layer to a 60 m floor. The dive begins with a black-water descent through clear freshwater, then at ~27 m a dense sulfide cloud appears as a milky river — divers see the crowns of long-dead trees and tangled branches rising up through it like a drowned forest. Punch down through the 3 m murk and the lower halocline opens into amber, anoxic salt water that smells like sulfur even through the regulator. Locals call it "The Nightmare." Sealed cenote with no cave overhead — open vertical shaft only, but the depth and stratified visibility make it a Level 3 dive in the Quintana Roo grading system.
Briefing note
Advanced Open Water minimum; most operators require Deep certification, prior Level 1 and Level 2 cenote dives, and 20+ logged dives. Bottom time below the sulfide layer triggers mandatory deco — plan as a deep dive. No sunscreen or insect repellent allowed in the water; rinse off at the shore shower before entry. Single tank dives only on a typical recreational profile; many divers run two tanks (sidemount or twins) for adequate gas reserves at 40+ m.
What you'll see
2 species curated- year-roundMosquitofish
- year-roundMayan tetra
Sightings evidence
1 record on file- high confidenceMosquitofish
- Last confirmed
- Apr 2026
- Recent records
- 130 within 10 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 We deliberately do not publish a numeric '% chance of sighting' from this data.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 | 24–25 °C | 30–50 m | none |
| Feb | 24–25 °C | 30–50 m | none |
| Mar | 24–25 °C | 30–50 m | none |
| Apr | 24–25 °C | 30–50 m | none |
| May | 24–25 °C | 25–40 m | none |
| Jun | 24–25 °C | 20–35 m | none |
| Jul | 24–25 °C | 20–35 m | none |
| Aug | 24–25 °C | 20–35 m | none |
| Sep | 24–25 °C | 20–35 m | none |
| Oct | 24–25 °C | 25–40 m | none |
| Nov | 24–25 °C | 30–50 m | none |
| Dec | 24–25 °C | 30–50 m | none |
Season calendar
Peak season highlighted · current month outlined
Next step
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