Deep diving on the President Coolidge

OK, all you serious divers look away, this blog is not for you!

Diving the SS President Coolidge is not for the faint hearted, these are deep dives with serious penetration (swimming inside the wreck).

Lets start with a few ship factoids!

It’s an SS – a steam ship – a luxury liner with rooms for almost 1,000 rich people! However, it was converted into a US troop carrier with 5,342 troops on board for use in WW 2, and sank as a result of hitting two (friendly) US mines. Apparently, the captain wasn’t given the information as to where the mines had been laid. Upon hitting the mines the captain drove the ship ashore in order to save as many lives as possible. He was successful, all but 2 people died.

Once all troops were off, the wreck slid backwards down the steep slope of Luganville harbour until it came to rest laid on its side: its deck plates vertical. Its bow sits at around 20m and stern around 70m.

It’s a BIG ship: nearly 200m long, and 25m wide makes for an extensive dive site!

All in all we do 4 dives and manage to see a small portion of the wreck.

Next diving factoids!!

The theory of diving, and dive tables and a bit of a blurb on diving qualifications and levels of experience. Feel free to skip ahead!

PADI Diving qualifications in order (as best as I can)

Qualification Minimum dives to achieve certification

Open water diver 4 dives

Advanced diver 9 dives

Speciality Courses There are a multitude of these which you can complete to extend your experience! (such as deep, wreck, night,

navigation etc)

Rescue diver 14 dives

Master Scuba Diver 50 dives (and 5 specialties)

Divemaster 60 (1st professional level)

Assistant Instructor (primarily theory based)

Open Water Scuba Instructor 100 - can teach open water to Divemaster

Specialty Instructor Can also teach specialty courses

Master Scuba Diver Trainer Can teach all of the above and is certified to teach 5 specialties as well

IDC Staff Instructor (Denise) Can teach divers to become Instructors (with a course


Master Instructor Has certified over 150 divers

Course Director Can independently teach Instructor courses

Instructor Certifier (Jamie) Examines Open Water Instructor candidates

(Jamies qualification is with SSI a different training agency)

Moving on........

Dive Tables

Recreational diving is guided by a set of tables allowing certain dive times to certain depths in order to avoid excessive accumulation of nitrogen (which can lead to decompression illness - the bends). Diving at depths beyond these tables also exposes divers to the risks of nitrogen narcosis and oxygen toxicity to name a few.

Nitrogen Narcosis

Nitrogen Narcosis is a relatively harmless euphoria experienced by some divers at deeper depths, although physiologically harmless it can impair judgement at depths and should be understood and avoided where possible.

Oxygen toxicity

This occurs at depths below about 66 meters .SCUBA tanks are filled with air not oxygen, however once past about 66m mark the partial pressures of oxygen become so high as to cause oxygen toxicity which causes convulsions and can be fatal. Diving beyond those depths requires specialised air blends and multiple tanks (beyond the scope of this blog).

Decompression Sickness

While breathing the compressed air underwater, nitrogen gets accumulated in our blood. The nitrogen then gradually gets absorbed into the tissues as the dive continues.

As we start to ascend, nitrogen starts getting dispersed from the tissues as a result of decreasing pressure.

 We need to ascend slowly as ascending to fast will reduce the pressure very rapidly. This can cause nitrogen bubble formation in the tissues and blood vessels. These nitrogen bubbles trapped in our body can result in Decompression Sickness.

Safety Stops

By doing a safety stop (after a slow ascent) we allow additional time for the nitrogen to be released slowly and prevent the formation of nitrogen bubbles in the blood and tissues.

Safety stops are considered best practice and we consider them mandatory for any dives below about 15-20 meters (or dives that are long in duration).

I will go into decompression stops later.

3 inch gun

Dive 1 is with Emily from Aquilon 3 and as she is an open water diver so we opt to do the orientation dive with her. The wreck is accessed by simply walking off the beach and swimming out (and down) about 100m to the bow. The access is fantastic with underwater lines set up so you can follow a rope directly to the bow.

“Orientation” is used loosely here as we drop down past the bow and follow the deck which is vertical to the sand (very disorientating trying to figure out what you are looking at) past anchor chain lockers and a 3 inch gun that sits on the deck.

Piles of ammunition, helmets and guns are also scattered around. At about the 30m mark we enter the wreck and proceed to explore a multitude of rooms and passage ways. As dive instructors we both remark afterwards about the size of the holes to squeeze through and the overhead environment that we are in. What does an overhead environment mean to a diver? No direct access to the surface, which if you get into any strife is a BIG issue. Usually, unless you have completed additional training in wreck penetration you would not consider entering an overhead environment. The training includes the use of lines and reels to increase safety. It is easy to disturb the silt that lies on every surface and this can become extremely disorientating, David our guide is excellent though and leads us competently through the wreck. These guides have done 1,000s of dives on this wreck.

Inside the President Coolidge

We proceed deeper and deeper into the wreck the only lights we have are the torches we hold in our hands. Disorientating is an understatement and when we finally emerge I am surprised to see that we have come out of the side of the ship (which is now the top due to its sideways orientation). We follow the starboard side back up to the guide rope and proceed up a very steep sandy slope to the “coral gardens” to do our safety stop.

The coral gardens have been built by Allen Powers Dive company for this very purpose and are fantastic, it is like swimming around in an aquarium and I am delighted to find multiple species of anemone fish, moray eels, octopus, nudibranchs and more. Our dive guide David also has some bread and proceeds to feed the fish. It is like being caught in a swarm of bees (in a good way) and I laugh a lot as the fish swim around me!!

Once the safety stop is completed we head back up to the surface - dive over. Diving the Coolidge has been on my diving bucket list since I first dove a ship wreck in Adelaide some 24 years ago. It was as impressive as I had hoped.

Dives 2,3 and 4.

Medical Supplies room

We dive again the following week with just Jamie and I, Emily and Aquilon 3 have headed of to New Caledonia. If I thought the previous dives were complex it is nothing compared to the next 3. We dive deeper and deeper and longer and longer, seeing the famous “lady and unicorn” statue and eventually the engine room. Depths ranging well above the 40m mark.

Now both Jamie and I separately have gone to depths just below 60m - but very briefly (1 minute at the most). And neither of us can recall a time where we dove for so long so deep. So finally, what is a decompression stop?

Decompression Stops

Unlike safety stops which are recommended (but not mandatory) a deco stop is an absolute. All recreational diving is calculated on always being able to do a direct assent to the surface at any time. Decompression diving effectively puts a “ceiling” on your dive. You MUST stop at certain depths for certain amounts of times. Luckily for us in this modern age our computers calculate this for us.

A decompression stop is a pause in a diver’s ascent made to allow the body to expel dissolved gases primarily nitrogen in the blood. Without decompression stops, these gases would expand, turning into bubbles and causing decompression sickness. While a safety stop is always carried out at 5m for 3 to 5 minutes a decompression stop varies based on the depth and time the diver spent at a particular depth. Decompression stops are a critical part of deep water diving. Typically, more than one decompression stop is needed.

As I said our dive computers calculate both the depths we need to stop at, and the length of time required. Amusingly they also tell you how much air you have left (in minutes) and how much bar (pressure of air - a bit like a fuel tank) you have left. And, a bit like a fuel tank that shows empty but allows you to continue to drive, the minutes of air left has a safety buffer factored into it. As a conservative measure a dive computer will commonly show that you are out of air (minutes left) while still showing you have bar left in the tank. This is not I repeat NOT an advisable level to get to. Most of the time Jamie and I will exit the water with 50 - 75 bar remaining. Not so on dive 4. Our 46m dive threw both our computers into significant decompression. The previous days had also been deco dives, but only for 5 to 10 minutes, today Jamie needed to do 30 minutes and I needed to do 25. As I glanced at my computer I had to chuckle, 25 minutes of decompression required- air time left 10minutes. Hmmm, that’s not going to work!!!

I was not concerned though as the dive company leave full dive tanks and regulators set up and ready to go at the deco stops. I stayed within 2 meters of the spare air, but as my fuel gauge (air gauge) still read at 34 bar I thought I would see just how long my air would actually last. Jamie went straight to the spare tank as his 30 minutes of deco was never going to happen on his 30 bar. As my time slowly ticked down and my pressure got lower and lower I was impressed to see that I probably was going to have enough air. Not only did I complete my own deco stop I stayed the extra 5 minutes to keep Jamie company. Once deco stops were completed we made our way to the surface. I excited with zero bar remaining!

That’s the Coolidge done, can’t wait to see what the Solomon Islands wreck dives have in store for us.

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