The Japenese Wreck

The Japanese Wreck

 About the wreck

  • WWII Japanese submarine patrol boat believed to be scuttled in 1945.
  • Simon Liddiard, owner of Blue Marlin Dive, heard the story from a local fisherman when he arrived on the island 20 years ago. He spent one month looking for it before he found it.
  • Only Trawangan Dive and Blue Marlin have the GPS coordinates for the wreck and as such there are relatively few people who have dived it.
  • The boat is about 20 metres long and 7 metres wide. It remains intact and in good condition.


  • The boat lies 1km off the coast of Lombok at a depth of 45 metres. It takes approx. 20 minutes to get to the site from Gili Trawangan.

 What’s there to see

  • Lion fish
  • Batfish
  • Snappers
  • Frogfish
  • Nudibranch
  • Scorpion fish
  • Moray eels
  • Sea fans
  • Barrel sponges
  • Bullets (50 cal browning machine) –
    Do not tap or take

Minimum experience

  • At a minimum, PADI Advanced Open Water or equivalent.
  • Ideally Nitrox (Enriched Air) certified. If this is not the case, it can be conducted as an Introduction to Nitrox and divers will be given an in-depth briefing about the use of Nitrox.

Ascents and descents

  • Once the wreck has been located using GPS, the boat crew will sink a line which should be used for ascents and descents.
  • Divers should descend using the line as a visual reference only and should refrain from pulling on the line, as this could drag it away from the wreck. At the most, use one finger to stabilise yourself. Do not descend quicker than the guide. Inflate BCD early and often during the descent – do not wait until you reach the wreck to begin inflating.

  • Divers ascend using the line and should hold the line in order to control depth during decompression stops. Do not ascend quicker than guide, but equally do not ascend much slower than the guide. Remember to deflate often to avoid a rapid ascent. Divers should remain at the same level or slightly below the guide.

Buoyancy control

  • Good buoyancy control is crucial on the dive to avoid damaging the wreck and to avoid stirring up the sandy bottom.

  • Avoid the bottom and take care when using the wreck to stabilise yourself. Take a good look and waft hand to ensure there are no scorpion fish around.

Staged decompression dive

  • Due to the depth of the site, the dive is a decompression dive. This means that there are ceilings to be respected upon the ascent, otherwise known as virtual overheads.

  • Decompression stops of varying times need to be made at each ceiling before ascending to the next in order to control the release of nitrogen from the body. Breaking any of these ceilings would mean there is an increased risk of developing decompression sickness.
  • The guide will tell you both before and during the dive at what depth and for long how you will stop for.

Gas mixes

  • Nitrox is used for the dive to reduce nitrogen loading and therefore decrease decompression times.
  • The optimum mix for the dive is EANx28 which, at a PPO2 of 1.6, gives an MOD of 47 metres. In fact, most of the dive is spent at 43m where the PPO2 is 1.48.
  • It is possible that a high percentage of oxygen, typically 80%, may be used in the drop tank. In the event that a diver requires the drop tank, the guide will ensure (s)he uses it at the appropriate depth.

Use of computers

  • The use of personal dive computers is NOT recommended on this dive. Different computer models use different algorithms to calculate decompression stops. This could lead to divers becoming separated from the guide upon the ascent which can be risky.
  • All divers will the use the dive plan prepared by the guide. The guide uses computer software to plan the dive and factors in a high degree of conservatism to suit a broad range of divers.

Safety procedures

  • Low on air
    A diver should signal low on air when they reach 70 bars. The dive will be aborted and all divers will ascend with guide.
  • Out of air
    A diver should approach their buddy or the guide and signal out of air. If the buddy, locate and breathe from alternate air source. If the guide, breathe from long hose and guide will switch to the short hose. It is important for the diver to stay close to the guide while breathing from the long hose. When they reach the drop tank, the diver should breathe from this.
  • Nitrogen narcosis
    Divers will undoubtedly experience some degree of nitrogen narcosis during the dive. Signs and symptoms include a loss of good judgment, a false sense of security, lack of concern for a specific task or for their safety, unjustified elation, drowsiness and a desire to sleep, or anxiety. In the event that the level of narcosis becomes uncomfortable, the diver should signal to the guide and the dive will be aborted.

  • Buddy separation
    It is important not to get separated on this dive. If the visibility is good, divers may explore the wreck at their leisure but they should not swim away from the wreck.

Signal review

  • OK
  • Problem
  • Ascend/descend
  • Level off
  • Decompression stop time
  • Narcosis
  • Strong current
  • Abort dive
  • Out of air
  • Low on air
  • How much air
  • Buddy up

Dive plan





















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