Toho Maru 4^o 53.078’ N  114^o 08.705’ E

26th November 1944

The strange story of how our home wreck the Toho Maru turned out to be the Yuho Maru!!

Wreckage lying about 17 miles north of Kuala Belait has been well known to local fisherman for decades. The wreck was precisely located by Shell's Topographic department  in 1970, however, the first divers to locate the wreck and dive her were Ed Ehlman and some friends in 1979. The discovery was reported in the Borneo Bulletin with the wreckage identified as the stern of the Toho Maru largely based on a report in Lloyd's list. 

It was the first of eight big wrecks offshore Brunei to be discovered and dived over the next 24 years, however, its location was forgotten as the first divers were transferred. Wreck locations in pre-GPS days were often casualties of vague transits and inconsistent local knowledge.  

It’s precise location is  4^o 53.078’ N  114^o 08.705’ E. (Please note that, like all Brunei Shell’s coordinates, the datum used here is Timbalai, not WGS84, and that we have quoted the coordinates in degrees : decimal minutes not degrees : minutes : seconds. Many fruitless searches for wrecks all over the sport diving world have been frustrated by the lack of these basic considerations).

In the Lloyd’s list of 2nd January 1982, there is a report of a wreck identified as the Toho Maru, sunk offshore Brunei at approximate location 4^o 55’ 00” N;  144^o 05’ 00” E. The wreck was sunk on 26th November 1944, two days before the Atago Maru of Piasau that was sunk in a bombing campaign conducted by the Australian Air Force. The wreck was described as a Japanese tanker of some 5,000 tons.

An early side-scan sonar survey conducted by the Topographical department of Brunei Shell identified the wreckage as a vessel lying on her port side with damage to the superstructure; bows bearing 302^o . The vessel appeared incomplete and scattered. The length and width appeared to be about 70 * 16 metres and the wreckage rose 14 metres from the sea-bed at 54 metres below chart datum.

ROV pictures taken subsequently identified solid structure at 41 metres depth.

The last three paragraphs provide strong corroborative evidence that the wreck is indeed the Toho Maru, however, there seem to be some odd inconsistencies. The wreckage sits upright and comprises the poop deck and after well deck of a small tanker. The wreck does indeed lie on a bearing of 300^o, however, there is no point higher than 45 metres (the barrel of the stern gun). However, with some consideration of chart datum (usually about 1.5 metres less than the measured depths on the wreck), the gun barrel lies at 43.5 metres, the sea-bed at 52 metres but there is a deep scour around the vessel to 55.5 metres. Indeed, the wreck does stand 12 metres proud of the sea-bed; just!

For many years, the club searched for the bow section believing that the ROV reports referred to a much higher standing piece of undiscovered wreckage. No other wreckage was found, nor is reported by Brunei Shell. The solution was given by Ed Ehlman over a conversation with myself and Pius Cagienard in 1997. Typically of compartmentalised tankers, the bows never sank and were towed to Singapore in 1944!

What remains is the heavily bombed stern of an approximately 5,000 ton tanker. It lies upright, and only the poop and after well deck are present. There is a distinct line across the ship forward of the gun where there is intense destruction and a huge hole on the starboard side. The line is probably a stern bulkhead. The ship is fairly well collapsed inwards forward of this line and there is another hole through the hull at what was the forward end of the engine room. There is no remaining superstructure; it was either blown off in the bombing or reduced by subsequent fire. The wreck has been colonised by all sorts of fish from small fry to massive groupers.

The modern sidescan sonar image (BSP below) agrees remarkably well with a drawing compiled from composite photographs taken from 33 metres looking downwards (Elder 1994 - The drawing was made before the side-scan sonar image was available).

Click on a yellow dot to see a photograph of the wreckage. All the shots were taken in natural light between 47 - 50 metres. The diagram above was composed from a mosaic of photographs looking down from 33 metres.

(John Elder and Mark Card - 20th August 1994).

The cat-walk lies, not on the vessel's centre-line, but over to port. This is typical of Japanese tankers of this period. Based on similar Japanese tankers (Shinkoko Maru and Fujisan Maru, Truk Lagoon), a rule-of-thumb can be proposed:-

gross tonnage = (length *width * draft in metres) * 0.37

Comparing the wreck of the Toho Maru's width with these other vessels (150 * 20 *9 metres for a 10,000 ton tanker), a tonnage of 3,400 to 5,000 tons depending on a width of 14 to 16 metres, can be pro-rated. This is in line with Lloyd's estimate.

In conclusion, the Toho Maru was a Japanese tanker of about 120 * 15 *7 metres of which only about a 50 metre length remains. The gross tonnage was about 4,000 - 5,000 tons and the bulk of the wreck lies some four metres above the surrounding sea-bed excluding the scour.

Diving the wreck

This is a deep dive that will take the diver below 50 metres. The club used to have a rule that the ascent was begun after 15 minutes from leaving the surface or 100 bar showing on either divers' gauge, whichever came first. These days, the Panaga rule is that each diver must carry an independent air source, the most common configuration being 2 * 11 litres. This has extended the bottom times to 25 minutes for the few divers who use a high Nitrox mix for decompression. Total dive run times are about 70 minutes. The club feels that this is a dive for PADI Dive Masters / BSAC Dive Leaders and above, who carry an extended range qualification and are dive fit. This applies to all our deep wrecks.

11th October 2003:

After three low vis. dives on the Toho this year, at last we were rewarded with decent visibility. There was a strong surface current flowing to the north-east, a consequence of the heavy recent rains from the Baram. Turbid river water with just a few metres vis. was present here 17 miles offshore and 25 miles from the Baram river mouth. Below 10 metres, the vis. increased dramatically and the current vanished. The presence of a large, and rather close, school of barracuda indicated that the wreck was nearby. Indeed, the powerful shallow current on the shot line suggested that the shot had hit the wreck and held. Below 27 metres, the entire wreck was visible. This is rare and a moment to be truly savoured. Arriving on the wreck at 49 metres we tied on a jump-line.

After 18 minutes, the ascent began with the computers indicating about 22 minutes of stops. I was carrying two computers and it was instructive to observe the differences between them. On my left wrist I carried a second generation Aladin Pro (mid 1990's); on my right, a Buddy Nexus. The latter was set to its 'conservative setting' and indeed, on arriving at the Buddy's first stop at 12 metres, 25 minutes of decompression was indicated against the Aladin's 23 minutes. However, the Buddy will handle two gas mixes and I had pre-programmed it to go onto Nitrox 80 at 7 metres. At this point with the Aladin still requiring 18 minutes, the Buddy dropped back to 11 minutes showing the effect of accelerated decompression. I actually did decompress on Nitrox 80, however, I did the full air stop, partly to stay with my dive buddy who was decompressing on air, and partly because of the extra margin of safety. 

In August 2004, we discovered that our home wreck, the Toho Maru, was in all probability the Yuho Maru!

September 4th 2004:  Toho Maru ??

We enjoyed excellent visibility down to the Toho, whilst large schools of pelagics swarmed above us. The width of the vessel was measured by Terry Dukes and Dave Outhwaite to be 16.5 metres. This suggests that the vessel was a 5,000 ton tanker (Yuho Maru Class) rather than the 10,000 tons of the Toho Maru Class. This was the third trimix dive made by Panaga Divers. Typically, divers are carrying a mix of 2,800 - 4,800 litres of 21% Oxygen, 25% Helium for the dive gas, with 1,400 litres of nitrox 70% for the decompression gas. A 23 minute bottom time on the wreck at 50 - 54 metres allows the divers to return to the surface 45 minutes after they begin their ascent. 

24th April 2005: 

Congratulations to Dale on his 300th dive which he kept secret until after the dive (as you should*). Large dolphins swimming in close groups of half a dozen enlivened the trip back to the KBBC. Thanks to an early arrival by our guests from further afield, we were out and back by 12.30. 

* I've a bee in my bonnet about 'special dives' as Dale and many others know. I'll mention it briefly here and perhaps, some day, expand about it in the Members' Pages. The very act of mentioning that this will be my X hundredth dive, immediately puts all the other divers under a perceived obligation to make it a real good one. Most laudable, however, when the weather picks up the day before and people say "We ought to cancel but it's old Fred's X hundredth dive, so we'll go for it", a willing entry of the incident pit is accepted, and I've seen it go wrong too often. Dale was quite right. Announce the achievement after the event, and let the marshal make his decisions unencumbered.

November 2006:

Terry Dukes, turned up some new and exciting information about the 'Yuho Maru' from a Japanese modeller. At last, we have a real photograph of the ship!

(Translated from the original Japanese by Kosuke Nishi.)

'Yuho Maru' - Iino Kaiun (The name of the ship-owner, Iino is the name, Kaiun means Sea Shipment)  5,226 tons

The ship was hit by torpedo at 04deg 54min north, 114deg 07min east, approximately 35 kilometres NNE of Cape Baram, north west offshore Borneo, at 16:11 on 26th November 1944.  She was towed to Miri port and arrived there, but sank at 04:00 on 2nd December 1944. All the 26 personnel on board were killed by the torpedo hit.

Very interesting! The location is definitely that of our wreck, however, only the stern (aft of the stern mast on the picture) lies there. The ship must have broken in two as did her sister ship, the 'Nichinan Maru No.2' that was torpedoed north of the Spratleys 18 days earlier. The remainder of the ship may have been towed to Miri, however, the tanker's draft of seven metres or so would not allow it within three km of the beach. I suspect the wreck was grounded whilst the Japanese decided its fate. On 28th November, the American air force bombed the Miri Roads (offshore anchorage) and sank the Atago Maru. Perhaps realising that the bows contained precious fuel, the Japanese decided to tow it out of harm's way to Singapore. Along the way, the bows sank, for today they lie nearly 200 km east of Singapore. Amazingly, the two parts of the wreck lie just over 1,000 km apart!

The Japanese modeller sent some more information about the Wartime Standard Type 1TM tankers. Twenty-six of these tankers were built by various yards including Hitachi, and Mitsubishi at Nagasaki. The dimensions of the vessel are 120 m long, 16.3  m wide and 9 m moulded depth, very close to our estimates from the past. The tonnage was 5,228 tons. The stern section is just over 50 metres long (58 metres on the port side). The distinctive features of these utility standard ships were the square section masts and the elliptical oil tank hatch covers (see sketch earlier in article).

The engine room lies forward of the boiler room. A mangled boiler is visible in the after of the two torpedo holes. Unusually for a merchantman, the 4,000 hp steam turbine that powered the Yuho Maru, lies in front of the boilers; the prop-shaft passing beneath the boilers to the stern. Perhaps this was to insert a buffer between the fires of the boiler room and the volatile cargo. Note how far aft the funnel (directly above the boilers) is placed compared to a conventional aft-engined cargo vessel. The top of the engine, that we have never seen, must lie deeper than 55 metres, and the Yuho Maru is a pile of collapsed metal at this depth. Sadly, the Japanese characters on the diagram are illegible.