Narcosis Colosseum is the 9th deepest technical dive site in the Gulf of Thailand, dropping down to a final depth of 50m. Being easily accessible this technical dive site is perfect for those looking to complete their Extended Range or Tec 50 dives.
NARCOSIS COLOSSEUM DIVE SITE LOCATION
Narcosis Colosseum Technical dive site is located in the Gulf of Thailand, Samaesan, in Sattahip District, Chonburi Province. It is one of the two holes that lies directly to the south of Koh Chuang that is seperated by a ridge at 30m. Out of the two it is the smaller, shallower northern site. It is surrounded on all sites by relatively steep slopes hence the name, colosseum.
NARCOSIS COLOSSEUM DIVE SITE HISTORY
The first recorded dive of this site was on 15th Jan 2026 by local Tec Instructors Ryland Cairns & Troy Jamieson. This dive was second in the series after diving the deeper site south of the ridge. The dive site’s name originates from the fact it is a steep sided 360° hole, much like a colosseum. With the site bottoming out at 50m it is ideal for Extended Range Tec Dives on air – allowing divers to experience some mild narcosis.
Conditions on the day were amazing. The dive took place roughly 4 hours after high tide at Sattahip – 0724hrs. Minimal current experienced, with great visibility 18-20m. It is not certain if conditions for this site are less extreme than Samaesan Hole or we just got it on a good day. Will update following more dives.
UPDATE: Following a few more dives in the vicinity it is recommended to dive in slack tide or have a vigilant boat crew and large DSMB for signalling. The current was absolutely ripping and we ended up 2km to the south east of the dive site after completing deco.
ABOUT NARCOSIS COLOSSEUM DIVE SITE
With a depth of 50m it is the 9th deepest technical dive site in the Gulf of Thailand. Like with the adjacent 1/4 Mile dive site schools of small fish were spotted. To the South-West the slope is steepest with rocky out crops.
Narcosis Colosseum – Hazards
- Depth: Narcosis Colosseum descends down to 50m. At these depths, air can be used to however narcosis will be apparent and gas density will be at 7.15g/L. If you are planning to explore and don’t have a DPV then consider adding a splash of Helium.
- Visibility: Highly variable visibility means that conditions can range from 3-20m. Hope for good, prepare for bad.
- Darkness: Similar to visibility, hope for good, prepare for bad. I have had conditions where it is pitch black at 30m and others with natural light at the bottom. Bring a torch and back up!
- Strong Currents: The area has strong currents, so check the tides times before you go as there are only few days each month where tidal conditions (on paper) are ideal. In poor conditions it is not uncommon to drift for 2km during deco. Ensure that you have a vigilant boat captain that will look out for and follow your DSMBs otherwise there is a very really chance you will be lost at sea.
- Down Currents: Not as strong or as common as in Samaesan Hole. But watch your depth and ascent/descent just to make sure.
HOW TO DIVE NARCOSIS COLOSSEUM
The site is only accessible by boat, which is roughly a 60min trip from Chong Samaesan. Considering how new this site is I would recommend reaching out to Tec Pattaya for experienced TDI, PSAI and PADI Tec Instructors who regularly dive in this area.
