1/4 Mile Mouthpiece Drop stands as the third deepest technical dive site in the Gulf of Thailand, reaching impressive depths of up to 75 metres. Easily accessible by boat from Samaesan, this site offers an excellent alternative for technical divers when conditions at the Samaesan Hole are not optimal.
DIVE SITE LOCATION
The 1/4 Mile Mouthpiece Drop 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 larger, deep southern site. It is recognised as the third deepest technical dive site in the Gulf of Thailand.
DIVE SITE HISTORY
The first recorded dive of this site was on 15th Jan 2026 by local Tec Instructors Ryland Cairns & Troy Jamieson. The dive site’s long name originated from a friendly DPV drag race (1/4 Mile), during which the cable tie from Troy’s regulator snapped causing his mouthpiece to drop and thus forfeiting the race.
Conditions on the day were amazing. The dive took place roughly 2 hours after high tide at Sattahip – 0724hrs. Minimal current experienced, with great visibility 18-20m. At 75m it was gloomy but torches were useful rather than essential. At this point it is not certain if conditions for this site are less extreme than Samaesan Hole or we just go it on a good day. Will update following more dives.
UPDATE 1 : Follow more dives at this site it is apparent that on some days the current can be absolutely ripping. After diving the Narcosis Colosseum we ended up 2km to the south east! Have a good boat crew and decent surface signalling device if you are not diving at slack tide.
UPDATE 2: It is not just mouthpieces that are dropped at this site! Doc managed to drop both his deco cylinders and new regs at the surface (Location: 12°30.0521′N, 100°57.2912′E ). If your find them please reach out to my friends at Dive Right.
ABOUT THE DIVE SITE
The deepest part of this site is from roughly 75m, this can be followed southwest along a gradually ascending sandy bottomed trench containing soft corals and barrel corals. A few schools of small fish were spotted. To the North-East is a steep ridge that separates this site from the northern hole (Narcosis Colosseum). Rocky out crops were present amongst the sand.
1/4 Mile Mouthpiece Drop – Hazards
- Depth: 1/4 Mile Mouthpiece Drop Drop descends down to 75m at its deepest part. Hypoxic Trimix is therefore a recommendation for most divers. At these depths, deep air divers will have potentially debilitating nitrogen narcosis to manage as well as closely having to closely monitor for Ox Tox.
- 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 75m. 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 AT 1/4 MILE MOUTHPIECE DROP
The site is only accessible by boat, which is roughly a 40min 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.
Best Time of Year to Dive 1/4 Mile Mouthpiece Drop
The technical dive season in the Gulf of Thailand is typically from November to April. Weather is typically cooler and calmer leading to improved sea conditions and better visibility (up to 20m). This coincides with the high tourist season so hotels and flights may be a bit more expensive. Whilst the Sharkfin Deep Drop can be dived all year round, in the low tourist season (May to Oct) weather conditions can be unpredictable. The seasonal monsoons bring wind and rain which ultimately means increased waves and poor visibility. You may be able to get a good deal on flights and hotels during this season but your dives may be cancelled or impacted. Just factor this in when deciding to go.
Optimal tidal conditions for diving 1/4 Mile Mouthpiece Drop
As well as seasonal variations it is also recommended to check local tidal conditions (Sattahip Buoy). There are typically 3-6 optimal dive days a month during Neap Tides where divers can get plenty of slack tide to dive in. Factor this in when planning your dive trip. The images below should clearly highlight which day is best to go diving. That being said it is possible to dive in poor tidal conditions, so maybe save the ideal day for the Samaesan Hole
