Local Weather
Diving the M2 Submarine

Having dived the M2 submarine a few times of the last 10 years, she is clearly deteriorating fast and the shots being dropped on her have created a number of large holes in her hull.


The current at the M2 can make it a very challenging dive. Slack time is usually short and around 30 minutes. 


M2 Submarine Dive Map
  1. Stern 
  2. Stern hydroplanes 
  3. “Disappearing” gun 
  4. Conning tower 
  5. Hanger & crane 
  6. Catapult ramp
  1. Bollard 
  2. Bow 
  3. Torpedo tubes 
  4. Bow hydroplanes 
  5. Propeller shaft and rudder

Start your dive by descending down the shot line, 8 out of 10 times the shot will be sitting on the bow section of the sub. Drop down over the side (note: the port side usually has more sea life) where there is less current and swim along about 2 metres above the sea floor. You will notice large holes in the hull, which is home to some very impressive large conger eels. The stern extends beyond the prop shaft (no propeller) and rudder.  


Swim up onto the stern platform and follow it along the top. You will cross the "disappearing" 3 inch gun platform (the gun is in its lowered position and therefore flush with the hull) and is easily missed. The next recognisable element is the conning tower. Swim around it and follow the hanger. The hanger is open and you can swim into it for few metres – not much too see. Turnaround and exit the hanger and follow the catapult ramp.


If interested, you can swim back, swim on top the hanger and take a look at the top of the conning tower, but at that point you are likely to start fighting the current, especially if you need to go back and try to go up the shot. We tend to ignore the conning tower and release our SMB when reaching the bow – as after about 30 minutes the current starts picking up.  We drift away and make our way up that way.


The M2 was belonged to a trio of World War I submarines – the M1, M2 and M3. The M1 sank in 1925 and the M3 was taken out of service once the M2 had sunk. The M2 was modified to carry a foldable reconnaissance airplane. In January 1932, the M2 left Portland for an exercise in West Bay, where she sank taking the entire crew of 60 souls with her.  They tried to raise her, but a sudden gale just as she was to hit the surface, meant she had to be abandoned once again.


There are two theories to her sinking:

  • Theory 1: The crew opened the hanger doors too early upon hitting the surface, trying to beat their airplane launch record
  • Theory 2: To conserve pressure to clear ballast tanks, they used the hydroplanes to maintain the sub balanced and afloat and “pump” the ballast tanks clear at the surface. A failure of the one of the hydroplanes would have made her “slip” under and the water would have rushed through the open hanger doors


More on wiki

M2 Submarine

Posted on 4/22/2012 by SDA Editor

M2 Submarine, a World War I submarine with an airplane hanger.

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Key numbers

Dive type: Wreck-submarine

Length: 90m

Depth:  36m

Visibility: 10m

Location: 50°35.59N, 2°33.97W 

Difficulty: 4 Stars

Dive: 4 Stars


M2 launching airplane
Dive Log

Download a free log book page of this dive

M2 Log Book