May I pick your brains for a moment?

[Lefty Writer]

Howdy from SE Texas (and Happy Friday!)

As you can see from my username, Lefty Writer, writing is a passion of mine. I've written several short stories, and maintain a (somewhat) current blog. I've finally decided to take the plunge and start on my first novel. I got my PADI Rescue Diver card in 2015, and have been enjoying the relatively "tame" wrecks like the C-53, Kittiwake and Oriskany. My next courses will most likely be the beginning tech diving classes, and onward from there. That's where you fine folks come in. I need your expert advice on a few points to ensure my novel is accurate and plausible.

My novel will have my main character doing a dive on a newly discovered wreck, and find some old vials of a pathogen. The character has just finished training to allow independent wreck penetrations from his instructor, who happens to be his recreational dive buddy. This character does all of this diving as a hobby, and is not interested in tech diving professionally. Diving will only be a small portion of the overall novel, but I want even the small parts to be as accurate as possible.

For the story purposes, this wreck is about 140 - 150 feet deep in the Gulf of Mexico and is relatively intact.

1. Would it be plausible if my character was trained on rebreathers instead of doubles? If so, what would be a suitable beginner rig? Something like the Poseidon Seven?
2. Regardless of system, would this be done with TriMix? I looked at my nitrox MOD table, and saw that Nx 25 might work. Yes? No?
3. Given this is in the Gulf of Mexico, would a dry suit be necessary, or could he get by with a 5 or 7 mil? He's a native born Texan, and dives primarily in the Caribbean. He's warm natured, and is generally tolerant of cooler water. Since I've only done safety stops (and a "deep stop" diving the O), a 3/2 was adequate for me. I have no basis for comparison for doing a long deco stop.
4. Anything obvious I'm missing?

I truly appreciate any insight you tech divers could provide.

Thanks in advance!

 

[dumpsterDiver]

The dive could be done on air with a wetsuit. In the end of summer the dive probably could be done in a t-shirt and in the winter a 7 mm would be needed. Personally, I think that the narcosis factor (from air or light nitrox) makes the dive more complex and "exciting" from a narration perspective. It is not so deep that helium is required, at least for many hard core recreational divers in the Gulf.

 

[divezonescuba]

Hello:

You could really spice it up by making the wreck a German sub or a wreck with some uxo. There was a great novel by a guy called McKenna or something like that that did something with a sub off of Louisiana.

I can help you with the TEC, gulf diving, and uxo issues if you go any of those routes.

 

[doctormike]

Since you are creating this world, you can adjust the dive parameters to fit the requirements of the plot. I would work backwards, staring with how long you want the diver to be on the wreck, and whether you want to have him spending time in staged decompression. There are programs to do this, but if you give us an idea of how long you want him to be in the wreck, we can tell you how much time he would need for the ascent and what sort of deco gas he would have.

Is the idea that this a newly discovered wreck but the identity (and hence the layout) is known? Is the discovery of vials an accident, or is that something he is looking for? Is he just going to be entering the wreck with no idea what the interior conditions are?

The bottom line is that the typical diver with technical training probably would have some wreck experience by the time the finished advanced nitrox and deco procedures. I may be wrong, but my impression is that many people taking an advanced wreck course are not tech divers. I took it before tech training, and there was no planned deco. So if your diver had just finished a wreck course, it would be pretty gutsy (i.e. stupid) to spend any significant time or depth of penetration in a completely unknown wreck. The initial internal exploration of something like that (particularly if it was large) would probably be done by very experienced wreck divers. This is not a purpose sunk, prepared wreck. Any part of it could collapse at any time, and depending on the era of the wreck there would be loose cables, debris and other hazards inside. So to combine a virtual and physical overhead on the same dive for a new wreck diver seems overly aggressive (unless that's how you want this guy to appear).

I think that a rebreather adds a level of complexity (to both diving and writing!) that isn't necessary for this story, but I'm no writer, so maybe I'm wrong about that. I know that there aren't "levels" in diving, but my personal training path was wreck -> advanced wreck -> tech -> rebreather and I think that's pretty common. If the plot is going to hinge on him being a newer wreck diver (not sure what you mean by not being interested in tech diving professionally), I would stick with open circuit.

I'm not trimix certified, but I would feel comfortable doing this on air. Some agencies (I believe GUE) require helium below 100 feet, but that's not typical for other divers. I don't think that the diver would bother with EAN25 ("slightrox"), since it's not that much less nitrogen than air, and at this level you wouldn't be worried about NDLs as much as you would about deco and gas planning.

 

[KevinNM]

The idea of trying to do a wreck penetration at 150 feet on air scares the crap out of me. From what I have read, the problem with trying to find something small in an old wreck is that as soon as you touch something inside the wreck you will tend to silt out the wreck, as the whole inside is covered with very fine silt that is easily stirred up. Even your exhaust bubbles can cause issues. And to find stuff on that kind of wreck seems to require you grope through the silty buildup.

But I'm hardly an expert. Narrow deep spots are not for me.

 

[RainPilot]

Hmmm. Im now intrigued....

From a rebreather point of view, the RAID Deco 50 course would allow normoxic diluent to that depth and deco up to 30 minutes, I think there are some literary benefits to going that way. Think odd noises in the wreck leading him to explore something and eureka, etc

Hiding from bad guys in the water while doing deco would be an interesting (and not done before?) aspect, think crawling up along a sloping bottom watching the computer and the bad guys with one eye each....

He would also be able to talk much more easily underwater so dialogue options are multiplied.

As far as making him a recreational diver, the prerequisites are 50 hours on CCR so not crazy to imagine a guy buying a Se7en and diving it with his buddy on shallow wrecks, gets the training and then goes on to this deeper wreck (accidental discovery while on a training dive ???)

If he was an experienced OC wreck diver then the aspects of silting from bubbles could be brought into play as a counterpoint.

The one BIG literary benefit from going CCR is that you have time. I HATE books and movies that have the diver doing 2000 things underwater for hours and Im asking myself how he managed to get a boat big enough for his tanks...

At least with CCR even the divers will be able to stop thinking about the timeline.

As a Poseidon diver (recreational) I suspect that I am the closest thing here to the path your character might take, all the CCR guys here seem to be highly tech qualified as well, Im not a wreck guy (yet, planning on training this year) so if there are any mindset / Rec CCR things I can help with by all means drop me a line, would love to help.

 

[NAM001]

If you are going to do 150 ft on OC then for the story you would probably be down for a while. so doubles would be the order of the day. large doubles. heavy doubles. each with buoyancy of say -1 to -15 empty and full. probably over filled 60% or so. That kind of rig for me calls for dry suit to rid yourself of neo suit compression and having a backup for the wing that in all stories has to get punctured exiting the wreck, fleeing from the giant mutant lion fish you disturbed in the wreck. that would call for trimix and perhaps a 25 or less/30 or more mix. that will keep the N2 well below 40-50% Even an 18% may be reasonable for the O2 and 50% for the He for the long duration. If you were doing a deliberate long dive then 10/50 may be of use and then the long deco to follow. 10/50 can make your N2 1/2 normal and you can go twice as deep to et to mod so that would be similar to a 75 ft dive giving what 50 min of what you would see as NDL on air. Tanks always open the avenue for low air crisis in the story. A RB will extend that time if you need it and still leaves open issues of crisis and bail out situations.

Some standard gasses are Between 30 metres and 48 metres we breathe 21/35 trimix. A little deeper we breathe 18/45 trimix. Deeperit's 15/55 trimix. decompression gases are equally standardised. 100% oxygen, 50% oxygen and 21/35 trimix are the three we use unless diving something genuinely extreme.

So there are things to work with.

 

[stiebs]

How familiar is your audience with the intricacies of diving? Are you assuming that the majority of readers won't know the difference, but you want it to be realistic if a tech diver does read it?

As many above have said, 140-150ft is about the max you would do on air, and even then your character would likely be very narced (possibly a good plot point) but would also have very little NDL to actually do any penetration before starting to incur deco.

Diving a rebreather using a hypoxic mix is probably more realistic for that type of dive in the tech diving scene, but I imagine a much wider range of audience can connect with air and small deco than with rebreathers.

If you want your readers to be introduced to diving beyond a "normal" experience, give him a rebreather, with a back story that gives him a good reason to have gone down the CCR path.

If you want to connect with more of your readers with familiar experiences, I reckon give him doubles, air, maybe a slightly shallower wreck (130 ft?) and some deco using EANx50.

 

[Diver0001]

1. Would it be plausible if my character was trained on rebreathers instead of doubles? If so, what would be a suitable beginner rig? Something like the Poseidon Seven?

No. If the character is a recreational diver he will not use a rebreather. They are advanced bits of gear that are very expensive to buy, expensive to train for and time intensive to use as compared to a BCD and a single tank. All of the people I know who have rebreathers are people who dive with trimix on a routine basis and use the rebreather as a way to keep gas costs down.

Similarly the training and expense involved in using doubles is not consistent with someone who only wants to dive recreationally although I see doubles as much more believable in your scenario.

2. Regardless of system, would this be done with TriMix? I looked at my nitrox MOD table, and saw that Nx 25 might work. Yes? No?

No. Getting the necessary training for diving with Trimix is again an expensive proposition that has equipment and procedural concerns and requires a level of dedication to the sport not consistent with the character being a recreational hobby diver. If I were you I would have the character diving on air, which creates complications that you can use to increase the suspense of the dives.

What you COULD do is have the character use doubles and Trimix using borrowed gear and "trust me" procedures. That could lead to all kinds of openings for **** hitting the fan that could create suspense in the diving scenes. Even if the character "gets away with it", the idea of using borrowed gear and trust-me procedures will give you all kinds of handles to make the scene interesting.

3. Given this is in the Gulf of Mexico, would a dry suit be necessary, or could he get by with a 5 or 7 mil? He's a native born Texan, and dives primarily in the Caribbean. He's warm natured, and is generally tolerant of cooler water. Since I've only done safety stops (and a "deep stop" diving the O), a 3/2 was adequate for me. I have no basis for comparison for doing a long deco stop.

I can't advise you well about this because I don't dive there very often. I've dived in the gulf of Mexico on several occasions (also at these depths) and a light wetsuit was sufficient. I've even dived there without any kind of exposure protection at all and found it comfortable enough. It seems unlikely to me that the character would need a drysuit in any case.

4. Anything obvious I'm missing?

If there is a penetration involved then most (technical) wreck divers have had procedural training. Again this kind of training is something that a recreational divers would be unlikely to have had.

By the way, I am someone who "discovered" (as part of a team) a previously unknown wreck. How we did that was to dive on the "question marks". Fishermen use a GPS system similar to what you have in your car but when they encounter an obstacle on the bottom -- something that catches their net and then needs to be avoided -- they mark it on their GPS system with a question mark to indicate that there is something there. This information is then shared so that other fishermen know to avoid that location.

As divers we also had access to this information and we went out a few times a year to dive on "question marks". What we often found was evidence of wreck (a bulge in the bottom with some steel sticking out) but on occasion we found something very interesting. For example, I was on the team that found the E36 -- a British E-type submarine that had been lost for something like 100 years.

How we approached identifying it could make a interesting side-line to your story. When we descended upon it we obviously saw right away that it was a submarine. We videoed and photographed all of the features we could find, we measured it's length, width and draft using "wreck reels" as measuring instruments and we went inside to remove some gauges to see what language the instruments were printed in.

Once at home it soon became clear because of the dimensions and the fact that it had dual rudders that it could only be an E-type. I then started a (tedious) investigation of how many E-types were made and where they ended up. By process of elimination I was able to determine which specific boat we had found.

I then informed the Royal Navy of our find, including the GPS coordinates, and received a letter back from them thanking us and warning us not to dive on that wreck because it was full of live torpedoes (which we already knew). They also informed us of their "rules" for diving on British war wrecks. Namely, that it was to be treated as a grave site. Nothing was to be disturbed or moved and no human remains were to be removed, photographed or videoed.

Maybe you can use some of that.

R..

 

[RainPilot]

Well, you do sort-of know one person at least that dives a RB without all the trimix stuff

A Poseidon MK6 will run you about 3000 USD lightly used. The recreational level training is pretty reasonably priced, in fact the whole point of RAID initially was to allow divers to start their training on CCR directly. If you factor in that the equipment doesn't change from OW1 to normoxic, so no upgrading wings and doubles and valve drills etc etc the whole cost from OW1 to Tec50 level would probably be comparable to someone buying their own tanks and then progressing in OC.

In my agency it is entirely possible for a solely recreational diver to have done all his OW courses on a RB and move on to the equivalent of Tec 40-50 all on a RB. The debate on whether this is a good idea or not is a different kettle of fish but it is quite plausible.