Vertical Wreck

The Vertical Wreck

Also known as Pak 1 or ‘The Koho Maru-5’

Written by Stephen Burton

(Gulf of Thailand)

Depth 42meters; Air, Nitrox, ‘recommended technical decompression diving only’

The X-Vertical Wreck's Pak1 or Koho Maru-5 in it's latest position on the seabed South of Ban Pae Beach, Rayong Province. Click for Hi Res 75KB Hir-res image. Sketch by Steve Burton at Mermaids Dive Center, Pattaya

The First Sinking…

The 25-year-old tanker owned by the PAK Line originally sank at WGS84 N11’41.9, E101’40.8 on Aug 25, 1996, 50 kilometers west of Koh Chang in Trat, on its way to Vietnam. From an interview with one of the three survivors, There were 10 people in the ship at the time of the sinking.  One survivor still works at the fish port in Bangkok.  He said that the sinking occurred at about 3.00 in the morning while the ship was in the midst of a fierce storm near the Cambodian border.  Most of the crew was sleeping in the main cabins near the stern; all the survivors were sleeping in a cabin near the bow.  The guy said he heard a loud noise from the stern and the ship sank swiftly.  All the crew in the stern cabins died. A local dive Center heard rumors of a large ship sinking a long way offshore, and chartered a boat to investigate it’s potential as a dive site. The ship had sunk in a most unusual vertical position, with it’s stern on the seabed 60meters deep and it’s bows just 5meters below the surface, in an area of sometimes outstanding 50meter plus visibility. This would indeed make a fine dive site. First dives revealed extensive damage to the bows, obviously caused by a substantial impact with a large vessel, and later rumored have been caused by the Thai Navy vessel involved in the initial search for the tanker after it sank.

Thailand’s Most Famous shipwreck – As she used to be (sigh!)

Thailands Most Famous shipwreck the Vertical Wreck, as she used to be. Click for Hi-res image 189Kb

As word of this outstanding dive site spread, for 6 years, divers from around the world flocked to Pattaya to visit this unique shipwreck. There was concern that someday the gas in the tanks though to be holding the ship up would escape and the vessel would sink, Instead, the opposite happened. Sometime during February 2001. The vessel re-floated with the bows initially protruding at least 6 meters out of the water, and off she went ‘sailing’ again, drifting in the Ocean currents off in the general direction of Cambodia. Divers on one of the last vertical wreck live-aboard trips were treated to the outstanding treat of being able to dive under the stern of the vessel at a depth of 50meters and look up through the rudder and propeller along the entire length of the keel to the surface.

The Vertical Wreck floats away toward Cambodia. Unique dives under the stirn of the vessel at 50meters looking up the entire length of the hull.

The Thai Navy moves in to sink it (again)

With the PAK-1 now drifting dangerously in shipping lanes, and with the vessels insurers apparently doing nothing, the Thai Navy acted quickly formulated a plan to remove this new hazard to shipping. Two large tugs and a warship or two for escort, dragged the vessel back towards Thailand to sink it in an area where it would not be a hazard to shipping. Eventually, a location for the sinking was designated a few hours sailing South from Mae Phim Beach in Rayong Province. The explosives experts moved in and planted charges. Admiral Oknit pressed the detonator button, but none of the original charges detonated. Explosives experts gingerly re-entered to re-set the now live charges. A second attempt to detonate the charges resulted in 1 of the 4 charges exploding, blowing off one of the massive 300ton LPG tanks. The net result was that instead of sinking, the vessel was now relieved of another 300tons, reared 20m out of the water. Cables were attached work went on, and eventually, and with considerable trouble they relieved the vessel of both its tanks and got it to sink.

Diving the PAK-1 at it’s new location

Latest Picture – March 2009

photo courtesy of David Poley

Information from January 2003

This is now almost exclusively a very technical dive site. Your average recreational diver will feel very unsure dropping down onto this shipwreck in bad visibility and high seas.

Depth to the top of the wreck 25m; depth to the sea bed=42m

Visibility 1-15m; Best choice of gas is Nitrox 28

Thermo cline at approx 25-35m. Very good(30m+) viz above Thermo cline.

Very shite viz(1-3m) below Thermo cline. Like most thermo clines this varies in depth and severity. It might not be there when you dive it, or its effects might be much worse. Take torches of course!.  Note that the main mooring line is connected to the bow. There is sod all of interest there, so look out for the crew quarters on descent.

The tip of the aft radar mast is sometimes visible at about 25m. Veer off to this bit before hitting the deck. The Aft crew area still appears painted white. The stern area of the PAK-1 is penetration mungus, and is an immediate gear off to get to the good areas. But now, with everything at beautifully reasonable depths, a twin set plus deco should see the average techie inside for 45mins plus. Watch out for silt!

 Since there is cock all of interest forward of the bridge apart from the empty silty holds which one might want to visit ‘for old times sake’  I would be tempted to manage the dive with a NITROX28 or NITROX 30 twin

set, plus a Nitrox 28 ‘hand carry in’ plus pure Oxygen for deco. Put up with the slightly high ppO2, if you want to examine the mud for a couple of minutes.

Dives into the holds could be confusing for the inexperienced. If you have any Muppets on your dive trip , get them to reel off before going into them big open holds. They’re full of silt and one miss-judged fin kick sends viz

down to zero with lots of overhanging superstructure for the un-initiated to get trapped under forever!

PAK-1 Design Drawings

Plan View showing deck layout(109Kb)

Side View from original construction drawings (376 Kb)

GPS Location

WGS-84 N12 05′ 32.5″ E101 40′ 56.7″

Latest GPS fix (18 Jan 2004)

North 12.05.504

East 101.40.931

The line on the bow is not there any more. These are the stern points which have one line on it at present. courtesy of Mr. Wayne Sutcliffe. at Siemens

Transport Systems, Bangkok.


Latest dive info:-  3rd May 2008:-

We recently visited the Pak 1 on a wreck exploration trip, thank you for the latest GPS co-ordinates as they were dead on,

unlike some of our fisherman’s co-ordinates. Just for an update there are no longer any buoys attached to this wreck.

 We have a lot of photos if you are interested as we had excellent viz and could see from the bow to the stern. We also found a couple of new wrecks on the 3day trip including one very large wreck.

Thanks for your great site, Name: David Polley, Managing Director, Scuba Evolution Dive Center mob: 081-152-8092

Wreck Documentation, external underwater surveys and engineering analysis by Steve Burton C.Eng.,

Wreck Penetration dive info:-      Fred Evans, UNOCAL

Article Text, Picture Sources and credits for this wreck Courtesy of:-

Stephen Blumenthal (deceased)

Commercial Diver Fred Evans (deceased)

Steve Burton    Tech Diver

Jamie Macleod    Tech Diver

Additional Information on PAK-1 – gas storage tanks recovery and sinking 5th April 2004

PAK one’s gas tank was sunk during a missile firing exercise and laid down in position N12’21.8, E100’25.9″ The tank(s) stick up approx 8 meters from the seabed