Side Story--Sea Swirl's Dive · 1:40am Feb 1st, 2014
Sea Swirl’s Dive
Special thanks to metallusionismagic for pre-reading
Disclaimer: I am not a diver. I have never used any kind of diving equipment. All the facts in this story are as true as my research could make it, but this is not meant to serve as a how-to guide—especially not the dive table.
The Suit
Standard Diving Dress—what I refer to as a ‘hard hat suit,’ has been around longer than you would think. The first known diving helmet dates to 1715, and diving suits were described as early as 1405. The technology for shallow-water dives would be easily within the reach of pony technology as I envision it, and would not require magic to work.
an early diving suit (1700s)
The theoretical maximum depth for a standard diving dress is six hundred feet, according to Wikipedia. This comes with great risks, which I’ll get to.
The basic concept behind the suit is high-pressure air is pumped in, equal to the pressure of the water outside. This both serves to give the diver air, and to keep the diver from being crushed by the outside pressure, which is much greater than air pressure. According to an online calculator, the water pressure at 180 feet is 78psi. So, as long as Sea Swirl’s suit remains pressurized to 78psi, she’ll be fine.
There are a couple of risks with the design of the suit. The first vulnerability is the air line. If it becomes severed, the end of the diver is gruesome. If you really want to know what happens, there’s an episode of Mythbusters where they test it. [Here’s the YouTube link; click at your own risk. Dive Suit Decompression] Of course, the suits have a valve to theoretically prevent this from happening, so the diver just has to worry about suffocating before she can be pulled back to the surface, where she’ll hopefully be placed in a decompression chamber (for reasons I’ll discuss below). Obviously, any tear in the suit will probably also be fatal.
For Sea Swirl’s suit, I have added the feature that she can drop her weight boots and weight saddlebags, and make a free ascent, if for some reason the winch breaks. It’s a nice nod to safety, but realistically on a solo dive, it probably won’t work. She’d have to find the shot-line on her own, slowly drop weights and adjust the air pressure in her suit so that she doesn’t rise too fast, and she’d have to know that she needed to do that. The only way Coco can signal a problem to her is if he shuts off her air in a prearranged signal, and she might not recognize that signal because of nitrogen narcosis.
Rapture of the Deep
The reason that divers on deep dives breath special air mixtures (like HeLox) is because of a phenomenon known as nitrogen narcosis. Basically, our bodies aren’t designed to handle high-pressure gasses. Ordinary atmospheric gases at high pressure act as a narcotic, and will make the diver ‘drunk.’ This is why recreational dives don’t go below 130 feet, in case you were wondering. Every diver reacts differently, but at her depth hallucinations, mental confusion, tunnel vision, and loss of dexterity would be very likely symptoms. This can be avoided in two ways—breath special mixtures (like HeLox), or ascend.
That’s one of the reasons that Coco is controlling the winch. At the end of her bottom time, he’ll just start winching her back up. Unless she cuts her own air line or the winch rope, or gets trapped inside something, she’ll come back to her senses as she rises and the pressure decreases. Unfortunately, there’s another problem she’ll face on the ascent, and that’s decompression sickness.
The Bottom
Visibility on the bottom is usually terrible. LIght doesn’t penetrate beyond about 50 meters in coastal waters. On top of that, all the stuff in the water can reduce that distance. Anyone who’s spent any time at all looking into bodies of water knows that there are some where you can clearly see the bottom a very great distance down, and others where you can’t see anything. According to a website about the Finger Lakes in New York, until the Zebra Mussel showed up in ‘89, horizontal underwater visibility was about 12-15 feet. To put that in perspective, if I were standing at the front of my Suburban, I would be unable to see the back of it. I’m assuming that the Ponyville reservoir has less industrial pollution, and therefore better visibility—but probably not all that much better. Not at those depths.
On top of that, Sea Swirl is wearing a weighted suit, and walking on the bottom with her weighted shoes. With each step she takes, a cloud of sediment is going to be kicked up, and since it’s very light, it will take it a while to settle. That’s why she has to use a metal-finding spell to help her; once she starts moving, the bottom will be largely obscured by the cloud of silt she’s trailing along with her.
The Bends
As the pressure on the body diminishes, the gasses trapped in the body expand and form bubbles. The symptoms of this are manifold, but one of the most common is extreme deep pain in the joints, which often caused divers and caisson workers to bend over from the pain. It can cause paralysis and death.
The good news is that this, too, is easily managed. If the ascent is controlled, most of the gasses have time to leave via the lungs, preventing the problem completely. Since there’s no point in Sea Swirl dying a horrible death, I’ll assume that the ponies know this. Since we’ve seen a large bridge with piers in the water in Rarity Takes Manehattan, the ponies probably figured it out after a few caisson workers (often called sandhogs) got crippled and died in agony. Unfortunately, that’s how we humans figured it out. For example, when the Eads bridge in St. Louis was built in 1871, thirty workers were severely injured by decompression sickness, and twelve died.
Decompression Tables
There are two ways to avoid the bends. One is to quickly ascend, and promptly be placed into a decompression chamber aboard the dive boat. This has the advantage that the diver can be monitored by a doctor, and any problems can be fairly easily managed when the diver is on the surface. Of course, if the diver doesn’t have access to a large ship, the only other option is to take decompression stops on the way up. That takes much longer than the bottom time.
Since recreational dives shouldn’t go below 130 feet, I had some difficulty finding the appropriate table, but I eventually managed. For Sea Swirl’s dive, here’s the ascent table:
Dive facts: Depth 60 meters (about
180200’)
65 minutes bottom time, 5 minutes descent (1 hour 10 min total)
Ascent decompression stops
05 min at 24 meters
10 min at 21 meters
15 min at 18 meters
30 min at 15 meters
40 min at 12 meters
45 min at 9 meters
45 min at 6 meters
50 min at 3 meters
Total ascent time 4 hours
This gives her a total working time of one hour, per five hours spent on the dive. But the bad news doesn’t stop there; she can’t go down again if she doesn’t find Dale’s glasses. Even after that four hour ascent, not all the bubbles are gone. She needs to stay at the surface for at least six hours before she can safely go down again, and she can’t fly on an airship for twelve hours. Realistically, it means that she can attempt the dive once per day.
Other Facts
According to Wikipedia, yellow, orange, and white are the best colors for underwater visibility, due to the way the water affects the light spectrum.
Zombies are mentioned by Spike in the episode Bridle Gossip, so they’re vaguely canon.
Coco Crusoe is the official name for an often-seen background pony.
I need to pay more attention. When I saw this blog and the associated story update I was thinking you were Demon Eyes Laharl and were going to tell a little story about his version of Sea Swirl. I was so looking forward to more character interaction with her!
But then is was "just" Onto the Pony Planet.
I liked it though. You always put such detail into your prosical musings. I do have to ask: when are the further adventures of wall repair pony going to be included? 
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Wall-repair pony shows up in the next side story, which is set between OPP chapters 7 and 8 (so, before this one). It's still needing editing.
Want a sneak peek?
You're welcome!
I wonder if Sea Swirl related to Star Swirl in any way? I know that sharing a last name does not automatically a descendant make, even if she's a unicorn, but that would be an interesting idea.
Also, that diving suit is just screaming "HORRIBLE PAINFUL DEATH" in every way imaginable... *shudder*
P.S. I promise I'm not stalking you, bro. I'm just always on FIMFiction and really really like your stories, which is why I'm always here early.
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It's possible (maybe even likely). I've noticed that Earth Ponies tend to share first names, and unicorns last--although since so many names are fan names, that's kind of a meaningless statistic (although it could mean that Coco Pommel and Coco Crusoe are related).
Some of the other early diving suits were worse. The first diving bells got their air by having it lowered to them in weighted barrels, which were retrieved by a diver and carried under the bell. I swear I'm not making that up.
I don't mind if you stalk my work online. If you show up at my front door and demand to see the next chapter, though . . . I might be a little concerned.
In the words of Button Mash: 'Uh... ok...'
More interesting tidbits about modern diving:
Breathing ordinary air, divers descending deeper than 60 meters (200, not 180, feet) run into increased risk of experiencing dangerous seizures (and worse) due to Oxygen toxicity. At those depths, tec divers switch to gas mixtures with less oxygen.
Hydrogen can be used in place of nitrogen in a trimix (helium-nitrogen-oxygen) gas. This is advantageous because the lower mass of hydrogen makes it easier to breathe. The mixture isn't explosive as long as the oxygen content is low enough, however the diver must make sure it doesn't mix with higher concentrations of oxygen while in their equipment.
As far as I know, diving computers have replaced the tables pretty much completely, even in recreation.
- Assist the diver before the dive, similar to the tables
- Assist the diver during the dive, calculating decompression stops for the current dive as necessary (or remaining bottom time at the current depth, if stops are to be avoided)
- Assist the driver after the dive, calculating remaining gas saturation and taking these calculations into account when planning or making repeat dives
This makes them both more permissive and safer than tables. Also, more convenient, as planning multilevel dives with tables is no fun.
I remember getting tunnel vision a few years ago, that was a really weird experience.
Thats his official name? jesus christ that's terrifying.
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I made the correction in the blog (I just ballparked, rather than actually convert). For my purposes, that dive table was close enough to accurate, and it probably wouldn't hurt to take a little longer on the decompression stops. Of course, I also don't know if pony lungs would be more or less effective at degassing; as far as I know nobody has ever sent a horse down in a diving suit.
I think the danger of Oxygen toxicity is why I decided on a less-than-200' depth. From what I was able to find in my research, that was deep enough to be a challenge, but shallow enough to avoid some of the more interesting problems with a really deep dive.
I think they have. Most references I checked didn't give any dive times, just mentioned a dive computer.
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I've had it in the sense of concentrating so hard on one thing that I missed another very important thing (which is often called tunnel vision, but it's psychological, not physical). I want to say it's task saturation, but I'm not sure that's right.
Anyway, one time it lead to being blindsided by a city bus (yes, your brain can ignore something that big if you're concentrating on something else), and the other time I got flanked by a cop during a training exercise (I was busy shooting her partner, and she got around my side).
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Wow, you have had the most amazing constellation of jobs in your life.
I was at a dance. It was crowded, the room was small and poorly ventilated, and I was wearing a wool three piece suit, not the smartest choice on my part. I love dancing, and that night was no exception. I danced so hard and so long that I began to feel very hot and exhausted. I decided to go to the bathroom to splash some water on my face. As I was walking to the bathroom, my vision narrowed down as a grey fog crept in at the edges, and I felt as if my legs were collapsing under me. Thankfully I recovered quickly, but it was still a pretty bizarre experience.
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More hobbies, really. Most of my jobs have been fairly mundane.
Huh, so I described tunnel vision accurately? Awesome!
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In my experience yes. Though It was less of a grey fog and more of an area of my vision that didn't seem to work any more, if that makes any sense.
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Yeah, that makes sense.
I didn't know there was a side stories section until today. Neat stuff. I would like to draw attention to one point of your most recent chapter however. As a signal for more slack on the line, Sea Swirl would fill a bag with compressed air, and let the inflated bag shoot up to the surface. I don't know how you envision this bag in your head, but if it were a sealed bag, or one which only had a small opening, it would explode before it reached the surface. This principle is especially important in underwater escape scenarios. If you were in a submarine, and tried to ascend from 180 feet deep while holding your breath, your lungs would pop. I imagine that it would be fairly easy to have an orifice, or a relief valve installed into the bag, or even just to have a bag with an open mouth. I just felt like sharing some relatively useless info.
If you want to see a sealed bag of air explode as it ascends, watch this video. The relevant bit is around 1:25.
Interesting tidbit, the survival suits used by the UK are also used by the US.
I was imagining that she only partially inflated the bag, like they do with some of the high-altitude weather balloons. I think that would work.
She could have a pressure valve in the bag, too, like the one in her suit. I think she'd prefer the first choice, though--as long as she didn't put in too much air, the bag would be fine.
Thinking back on it now, the easiest way for her to make such a bag would be two squares of fabric sewn together with one of the corners cut off to let in air. A piece of twine with a weight, a few links of chain, or even something sewn along the bottom would make sure it rose right-side-up, would be easy to make and use, and she could carry dozens of them.
I had thought that she might send the glasses up in a similar manner, but then figured she would consider it too risky--if something went wrong on the way up, they'd never find the glasses again.
Now I'm pondering the less realistic side of things. Wonder if Pegasus ponies can handle decompression easier. Their biology(/magic) has to handle high altitudes and dealing with high speed maneuvers and maybe even extreme pressure differences in weather systems. Kind of moot since I imagine it would be pretty much impossible to get a Pegasus in a diving suit and underwater.
For unicorns, can't help but think about the use of magical shields instead of diving suits. Just a hemisphere of magic or some such. Which falls under the category of wild speculation since you'd have to throw physics out the window. Still interesting to think about. One though that occurred to me was maybe a magical shield maintained from the surface can avoid decompression problems (perfectly magic airtight and equalized pressure on the inside) but has the side effect that all the stress is placed right on the Unicorn's magic conduit/circuits/chi and that has the same mental/vision effects as the physical version. Which would be even worse since the focus of the Unicorn is what is keeping the shield in place. Going with a suit is probably for the best, but I can't help but think that Shining Armor could whip up some kind of shield that would work really good. Then again, he is powerful enough he could just create a barrier-walled tunnel from the shore down to the bottom and walk.
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Thing is, extreme weather pressures in air have nothing on water. At ground level, air pressure is about 15psi. Presumably, if a pegasus could fly all the way into space, it would encounter a pressure of 0. At the depth Sea Swirl is diving, water pressure is about 87psi.
That's not out of the range of possibility for some marine animals; I don't know who has the record, but there are certainly sea creatures which can dive well below the 200' mark or go all the way to the surface. Wikipedia tells me sperm whales can dive to 7400 feet, which is an eye-popping 3200psi. But I don't think a pegasus could. Seaponies, maybe.
I'd be willing to bet claustrophobia is common among pegasi.
If it was open on the bottom, you'd still have pressure issues. There's no technical reason you couldn't make a diving bell that took a diver down hundreds of feet, but of course you'd still have the decompression issues. Remember, decompression was first noticed in sandhogs, not divers. Possibly if it were an enclosed bubble, you could have the inside at a comfy one atmosphere, regardless of depth.
The other thing is that the strength of the shield is proportional to the unicorn's talent. Shining presumably has a talent for it, going by his cutie mark. Twilight is an exceptional magic user, and Cadance is an alicorn. I think that most unicorns couldn't produce much more than a head-sized bubble. I'm not sure what the effects of breathing in such a bubble would be; possibly a spell could 'scrub' the air so it was always fresh. Physiologically, I have no idea how/if that would work. I know there's a limit to how deep you can use a snorkel, and I would imagine a similar limit would be in place for a bubble of unpressurized air vs. pressure on the chest/lungs.
If the spell were a column, perhaps. Sort of a long tube extending down into the bottom of the lake--no reason why that wouldn't work. The water would have to be removed after the spell was cast, probably, but then the 'diver' could walk around in the clear area, and perhaps the spellcaster could move it about.
Twilight might be able to, as well, if she knew the right spell. But, from a writer's perspective (and a reader's, as well), there's no fun in a story if everything can be solved with a spell or two.
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But think of the potential! "Shining Armor, you have to stop protecting the entire kingdom for a day because we lost something at the bottom of this lake over here."
Hmm. I wonder if teleportation could have a equivalent of pressure sickness. Like fabric of space/time is subtly different in different places and nobody notices because physically moving there allows you to gradually adjust. So long-distance teleportation is impossible and you have to do several shorter jumps and pause between them to adjust.
As I said, with magic a author can kinda end up just fiddling with physics to get whatever result desired. I coming up with magic concepts that move problems around instead of just solving them *poof*. Or sets up interesting conflicts. Such as Pegasus ponies being physically perfectly suited for deep-sea diving, but will never ever go down there because of well understood psychological reasons. Hmmm.... Daring Do story concept in there somewhere. Anyway, I was thinking less altitude and more that we've seen Pegasus ponies create tornadoes that can lift and carry large amounts of water long distances. Gotta be some weird air pressure stresses going on there. Or, alternatively, Pegasus ponies might just have some magic in their respiratory system for reasons other than pressure. Such as breathing in thin air or in intense winds.
I'm not questioning the accuracy or physics. You always do a wonderful job at research and I learn something new with pretty much every author's note blogpost you put up. Just like to speculate.
Taking a glance at the Wikipedia entry for Tornado while writing this led me to this wonderful bit:
No area is safe from tornadoes. If you piss one off it will hunt you down!
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I think relative motion is more of an issue. Over short distances, it's not a problem; over long distances, it can be, especially since it appears to be able to be carried through a teleport. The spell can dampen it, but that takes more energy.
I think that's why Celestia does her long-distance teleports in and out from the air. It's more forgiving than the ground.
In Arrow 18, it turned out that unicorns were better suited to microgravity than pegasi.
Yeah, magic has to have some limitations. Even Twilight acknowledges it, and it's one of the reasons that Pinkie Pie frustrates her so much--not only does she operate outside the known limitations, but she doesn't even seem aware that she's doing so. It's an Earth Pony thing.
Hmm, sucking the lake dry might be a possibility with enough pegasi, but then where will the glasses wind up? Plus if the reservoirs in Cloudsdale are full, than all of Ponyville is going to have an unexpected rainstorm.
In the early eighties, a tornado went through Kalamazoo. It went up the ramp from US-131 to Main Street, which it followed all the way to Comstock. Amazingly, only five people were killed.
Oxygen-toxicity, Nitrogen-Narcosis, and the bends all comspired to kill Miss Seaswirl.
Beyond 60 Meters (200 Feet), one needs HeliOx and 1 of the last swallow-water stops on the way back to the surface (decompression can take someteen hours) of pure O2 for flushing the the remaining bubbly gases from her body —— Only as part of decompression, only at less than 10 meters, and only for less than 1 hour. ¿Do ponies have the technology for HeliOxDiving yet (they may not have yet discovered Helium)? or ¿are they limited to compressed air? If the ponies do have not discovered Helium, ¿do they use HydrOx for deep dives (Hydrogen/Oxygen-Mixture, but potentially explosive?
Unless one is a pony-eating Siren, ¡diving is very dangerous!
Go go gadget necropost!
This post brings back memories of when my da and I scuba dived together.
One of the really weird things (recreationally) diving at depth is how the pressure affects your perception of time. This was hammered into us as a safety warning by our instructors as you could easily inadvertently exceed your safe dive limits (or air capacity) if you did not continually monitor your dive clock. I will never forget the demonstration they did on our first deep dive ("deep" as defined by "near the maximum depth you can descend to without requiring a safety stop on the ascent"; approximately 25-26 metres). They gave us a simple 4 letter combination lock (combination D-I-V-E) and timed us unlocking it on the boat with a stopwatch. Every one did it within a few seconds as you would expect. We then descended and faffed around a bit, looking at all the pretty fish and corals and whatnot before the instructors took us aside and had us unlock the locks a second time. It felt normal, but I was shocked to see over 20 seconds had elapsed on the stopwatch
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I remember those tables! Lots of fun flipping back and forth on those, planning out multiple dives in a day. Or even more fun learning how to calculate the conversion factors for the standard blue table to both the yellow and white nitrox tables. Brings back some serious memories that...