Cenote Sac Actun, Tulum: The Sistema Sac Actun Cave System

What Sistema Sac Actun is

Sac Actun is a network of flooded passages in the limestone under the Tulum area, mapped by cave divers over decades. Its length depends on the date and on who is counting, so we use one dated survey figure and list the others. As of January 2023 it was the second-longest surveyed underwater cave system, behind Sistema Ox Bel Ha at 435.8 km; the two have traded the title since Nohoch Nah Chich was joined to Sac Actun in 2007. Its deepest point is 119.2 m (391 ft), at The Pit near Dos Ojos (Wikipedia).

• 386.1 km total, 378.6 km underwater — Quintana Roo Speleological Survey, 10 January 2023, as reported by Wikipedia.
• 347 km and 248 cenotes — Reuters, February 2018, after the Dos Ojos connection.
• 263 km plus 84 km — Sac Actun and Sistema Dos Ojos before the Gran Acuífero Maya project, led by Robbie Schmittner, found the link in January 2018.
• 228 cenote entrances — Wikipedia; Reuters gave 248 in 2018.

What lies inside the system

The caves were dry during the last Ice Age and flooded when sea level rose about 100 m at its end, which preserved what was inside (INAH, via Reuters 2018). Reuters reported about 200 archaeological sites in the system, about 140 of them Maya. In Hoyo Negro, in the connected Sistema Aktun Hu, divers found a mastodon at about 60 m and a human skull at 43 m (Wikipedia). More on the Maya side in what cenotes were used for and on the geology in how cenotes are formed.

Which cenotes open onto Sac Actun

Only a handful of the 228 entrances run as visitor parks. These are the ones our sources tie to the system. Dos Ojos on the Sac Actun system is the easiest place to see the cavern from the surface.

• Gran Cenote — About 5 km west of Tulum, where exploration began. Swim and snorkel; about 500 pesos in 2025–2026 reports.
• Dos Ojos — 20 to 22 km north of Tulum, joined to Sac Actun in 2018. Swim, snorkel and cavern dive; 350 to 500 pesos in 2026 reports.
• The Pit — In the Dos Ojos park; divers only, with Advanced Open Water plus a deep-diving qualification at one Tulum dive shop.
• Cenote Sac Actun and Nohoch Nah Chich — Listed by Tulum Times as tour-only sections that need a certified guide.

Visiting Sac Actun: swim, snorkel or dive

Most visitors see Sac Actun from the water at Gran Cenote or Dos Ojos, in the lit areas where you can see the way out. Cavern dives stay in that daylight zone; dive shops at Dos Ojos ask for at least Open Water certification. Cave diving goes past the daylight and is technical diving: training usually runs Cavern, Intro to Cave, Apprentice and Full Cave, and the rules include a continuous guideline to the exit, gas planning by thirds and at least three lights (Wikipedia). Read cave diving in cenotes before you book anything deeper than a cavern dive.

Getting there and booking

Tulum is about 130 km south of Cancún. ADO buses take about 2.5 hours and cost 250 to 300 pesos from downtown Cancún; the Tren Maya takes 1 h 32 min to 1 h 43 min. Gran Cenote is 4 to 5 km from Tulum on the Cobá road, and Dos Ojos 20 to 22 km north on Highway 307. Guided snorkel days and private cenote guides are compared on our cenote tours page, and certified divers will find the dive centres there too.