I need an expert ...

[Sue-ba]

I am a writer, (some critics may disagree--ha ha :blush. My latest romantic story involves diving. I have a little over 200 dives so have hopefully not disgraced myself so far, but there is a critical scene where I need an accident. However, my experience is purely recreational so I don't have the knowledge or experience necessary to make the scene believable. I've tried researching online but after a couple of wasted hours, I have decided to come to you, the experts. Any takers?

Let's say a brand new diver's BC won't hold air. One of her dump valves is tangled and in constant "pulled" position. (drawn from personal experience though I was able to remedy the problem without incident) She is too new to know what is happening and before she knows it, she is panicked and sinking. It takes a minute for anyone to notice and the hero has to save her. (Sappy, I know but it sells and a girl's gotta make a living).

How deep would she have go--she wouldn't be at her max depth for long, only until he reaches her and has to bring her up with his superior knowledge of diving and understanding of deco limits, etc. You know, the usual hero stuff. It has to be deep enough to require more than the standard safety stop but not put either of them in the hospital or chamber because ... he knows what he's doing.

Can anyone give me some details that would be realistic? Maybe not realistic--remember, sappy romance story at work here, but at least real enough to not embarrass myself entirely. How deep would it have to be and how long will it take to come up safely? (The captain of the boat could drop more tanks at different depths if necessary since she obviously panicked and blew through air)

Thank you very much!

 

[Nirvana]

I most certainly would not call myself an expert, but here goes my take on your story.

If I understood correctly, your scenario is that, soon after the dive starts, the girl has a problem with her BCD that she can't solve and she starts to sink before anyone can help her. Only after a few minutes the hero gets to know what has happened and goes after her. He finds her and helps her return to safety, doing some deco stops on the way.

In this case, the most serious risk to the girl is drowning, either because she panics and drops the regulator or because she runs out of air. I don't think her drowning would fit the story, so she must be found before her air supply ends. She would be very anxious, meaning her RMV or SAC would be high (let's say 1.8 ft3/min). This represents a certain problem for the story. Because she would have to be found soon, as her air would not last long. This would mean, in turn, that she would not spend a long time at the bottom, meaning very little deco (if any at all). Even descending at 100ft/min and reaching 200ft, a total of 5min from surface to bottom, with that SAC, would demmand 99ft3 (more than an Al80 can provide). The deco required, however, would be of only 3min at 20ft (V-Planner, VPM-B +3). If you want her to have to do some significant deco, she would have to breath calmly or have lots of air available, so she can be longer at the bottom. 15min bottom time would require 40min of deco (on air), and is achievable with a SAC of 0.5ft3/min (and another cylinder near the surface, thinking of single Al80).

I hope I have been of help. Best of luck with your writing.

 

[Searcaigh]

Can anyone give me some details that would be realistic? Maybe not realistic--remember, sappy romance story at work here,

So I guess a Warhammer manoeuvre by the hero is out of the question during the deco stop even if he had a curry the night before

Sorry Sue I could not resist

 

[boulderjohn]

I am actually in your shoes--I have a draft of a novel that includes an undersea problem, and I wanted to make sure that it was true to fact. In order to do that, you will need to fly in the face of some common fears. I suggest you have her in the grip of some of those common fears. Here are some random thoughts.

First of all, the more likely scenario is that there is a physical problem with a dump valve. I recently had this happen in a cave. I was borrowing an old doubles wing from someone else. As I ascended near the end of the dive, I reached back to the rear dump, pulled the strong, and the entire dump valve broke off in my hand. The plastic screw mechanism was totally rotten. My wing emptied quickly. Your damsel in distress could have a problem like that and sink out of control. Your hero could catch her and do the proper thing--turn her body in a position so that the faulty valve was not the highest point. This would allow her BCD to hold air and help with the ascent. IN my case, I was lucky to be in the final stages of the dive, so I needed very little air in the wing to begin with. I was also not in a silty environment, so simply dropping my knees put the air in the shoudler area, where it would not come out. Your situation would be about the opposite--putting the diver into a horizontal trim would mostly solve her problem.

Decompression Sickness: If your damsel in distress dropped pretty deep, was saved and helped to the surface, she could have a real concern about DCS. Being a beginner, she would not know what to do about it. The hero would know how to deal with it, either by knowing how his computer works for that problem or using another system to calculate the ascent. A quick plunge like that fairly early in the dive will not put her into a significant need for decompression. She won't know that, but he will.

Loss of Air: If she is inexperienced, she is panicked and breathing heavily. As pressure increases, she will go through air more quickly anyway; with panicked breathing it could become extreme. Your hero will be calm, will reassure her, will share air, etc.

Fear of CNS toxicity: If she is diving nitrox, she will drop well past her MOD, and with only a basic nitrox training, she will be terrified that she will get CNS toxicity and go into convulsions. Your hero will know how unlikely that will be, and how deep and for how long you actually have to go past the MOD before you are in danger. A person in her situation will almost certainly not have a problem.

Over-weighting; If your diver is sinking out of control so rapidly, she is over-weighted. Your hero might drop her weights. If she has a wieght integrated BCD, he might drop one of her pockets to try to get her closer to proper weighting. A diver on a recreational dive in warm water with (say) a 3mm wet suit should need very little air in the BCD to get neutral. A diver sinking out of control because of a loss of air in the BCD is very much over-weighted.

 

[Hawkwood]

I am actually in your shoes--I have a draft of a novel that includes an undersea problem, and I wanted to make sure that it was true to fact. In order to do that, you will need to fly in the face of some common fears. I suggest you have her in the grip of some of those common fears. Here are some random thoughts.

First of all, the more likely scenario is that there is a physical problem with a dump valve. I recently had this happen in a cave. I was borrowing an old doubles wing from someone else. As I ascended near the end of the dive, I reached back to the rear dump, pulled the strong, and the entire dump valve broke off in my hand. The plastic screw mechanism was totally rotten. My wing emptied quickly. Your damsel in distress could have a problem like that and sink out of control. Your hero could catch her and do the proper thing--turn her body in a position so that the faulty valve was not the highest point. This would allow her BCD to hold air and help with the ascent. IN my case, I was lucky to be in the final stages of the dive, so I needed very little air in the wing to begin with. I was also not in a silty environment, so simply dropping my knees put the air in the shoudler area, where it would not come out. Your situation would be about the opposite--putting the diver into a horizontal trim would mostly solve her problem.

Decompression Sickness: If your damsel in distress dropped pretty deep, was saved and helped to the surface, she could have a real concern about DCS. Being a beginner, she would not know what to do about it. The hero would know how to deal with it, either by knowing how his computer works for that problem or using another system to calculate the ascent. A quick plunge like that fairly early in the dive will not put her into a significant need for decompression. She won't know that, but he will.

Loss of Air: If she is inexperienced, she is panicked and breathing heavily. As pressure increases, she will go through air more quickly anyway; with panicked breathing it could become extreme. Your hero will be calm, will reassure her, will share air, etc.

Fear of CNS toxicity: If she is diving nitrox, she will drop well past her MOD, and with only a basic nitrox training, she will be terrified that she will get CNS toxicity and go into convulsions. Your hero will know how unlikely that will be, and how deep and for how long you actually have to go past the MOD before you are in danger. A person in her situation will almost certainly not have a problem.

Over-weighting; If your diver is sinking out of control so rapidly, she is over-weighted. Your hero might drop her weights. If she has a wieght integrated BCD, he might drop one of her pockets to try to get her closer to proper weighting. A diver on a recreational dive in warm water with (say) a 3mm wet suit should need very little air in the BCD to get neutral. A diver sinking out of control because of a loss of air in the BCD is very much over-weighted.

Nice!

And our hero will be Dirk Pitt.

 

[Sue-ba]

Nice!

And our hero will be Dirk Pitt.

That would be my choice, but I don't think Clive would appreciate it.

 

[Slamfire]

Ok, here goes my try.

Damsel is somewhat petit giving her a naturally low-ish SAC rate despite her being a newbie. She is diving an Al 80 tank with air. She is AOW (so that she is allowed in a Charter to dive a wreck like the Spiegel Grove) newbie with 12 dives under her belt. This is realistic because my instabuddy on my dive to the Spiegel Grove had this certification and experience level. Spiegel Grove sits in 130 ft of water but it is common for divers to stay at 80ft to 100ft for most of the dive.

Hero is diving double Al 80s because that is what he likes. He likes the balance. He just sets up his rig once for two boat dives. No exchanging of tanks during surface interval. And he likes the redundancy. This first dive of the day goes uneventful for 20 mins that Damsel spent at an average of 100 ft. Her computer says she's almost out of NDL time. So she starts to ascend. She saw Hero venting gas from his wing without breaking trim by pulling on the OPV valve. She gives it a try herself as she is ascending and hears a metallic snap following by rapid emptying of her BC and loss of bouyancy. She fell outside the wreck all the way to the 130 ft bottom.

About a year or 2 ago, several manufacturers (Halcyon, Dive Rite, Hog, etc) issued a recall on OPV valves that had a spring that could easily corrode and break. Damsel just happened to dive a BC with one such spring.

Damsel is starting to panic. This brings her normally lowish sac rate of 0.4 cu ft per min to 0.7 cu ft per min for the entire dive (including the non-emergency first 20 mins). Then she finally remembers that she can drop weights. Just as she is getting ready to drop weights Hero's steady hand comes over hers to prevent her from becoming a polaris missile to the surface. Overall Damsel spends a total of 5 additional minutes at 130ft.

Hero turns her body in a position where her bc holds air and starts taking her up. He checks her SPG and decides to put her on his long hose before she actually starts feeling an empty tank. He looks at his computer and SPG and makes some quick calculations. He pulls out a yellow SMB that has a little slate with a small pencil at the top. He writes "Send O2 for 2" and deploys the SMB while Damsel clings to his side (I know people who have had to write "Need O2" on a slate). He makes a 2 min stop at 40ft and another at 30ft. At 30ft a crewman from the boat joins them bringing 2 Al 40 tanks labelled Oxygen. At the 20 ft stop Hero grabs a regulator from an Al 40 and gives it to Damsel. Then Hero grabs one for himself. They do three mins at 20 ft and three more mins at 15 ft before they finally ascend.

Here's an applicable deco schedule with gas consumption figures:

MV-Plan 1.5.2
Settings: GF=30-80 Factors:1.0/1.0 ppH2O=2.041 ftsw ZHL16B
=========================================================
DESC: 99ft for 01:30 [ 2] on Air, SP: 0.0, END: 99ft
DIVE: 99ft for 18:30 [ 20] on Air, SP: 0.0, END: 99ft
DESC:130ft for 00:28 [ 20] on Air, SP: 0.0, END:130ft
DIVE:130ft for 05:00 [ 25] on Air, SP: 0.0, END:130ft
ASC : 50ft for 02:25 [ 28] on Air, SP: 0.0, END: 50ft
DECO: 50ft for 00:06 [ 28] on Air, SP: 0.0, END: 50ft M-Value: 63% [02], GF: 40%
DECO: 40ft for 02:00 [ 30] on Air, SP: 0.0, END: 40ft M-Value: 70% [02], GF: 50%
DECO: 30ft for 02:00 [ 32] on Air, SP: 0.0, END: 30ft M-Value: 75% [02], GF: 60%
DECO: 20ft for 03:00 [ 35] on Oxygen, SP: 0.0, END: 0ft M-Value: 81% [03], GF: 70%
DECO: 10ft for 03:00 [ 38] on Oxygen, SP: 0.0, END: 0ft M-Value: 83% [04], GF: 80%


Gas estimate based on Dive RMV =0.7, deco RMV =0.7cuft/min
Air : 85.5cuft
Oxygen : 6.1cuft
Oxygen Toxicity - OTUs: 29 CNS: 16%

 

[Sue-ba]

I most certainly would not call myself an expert, but here goes my take on your story.

If I understood correctly, your scenario is that, soon after the dive starts, the girl has a problem with her BCD that she can't solve and she starts to sink before anyone can help her. Only after a few minutes the hero gets to know what has happened and goes after her. He finds her and helps her return to safety, doing some deco stops on the way.

In this case, the most serious risk to the girl is drowning, either because she panics and drops the regulator or because she runs out of air. I don't think her drowning would fit the story, so she must be found before her air supply ends. She would be very anxious, meaning her RMV or SAC would be high (let's say 1.8 ft3/min). This represents a certain problem for the story. Because she would have to be found soon, as her air would not last long. This would mean, in turn, that she would not spend a long time at the bottom, meaning very little deco (if any at all). Even descending at 100ft/min and reaching 200ft, a total of 5min from surface to bottom, with that SAC, would demmand 99ft3 (more than an Al80 can provide). The deco required, however, would be of only 3min at 20ft (V-Planner, VPM-B +3). If you want her to have to do some significant deco, she would have to breath calmly or have lots of air available, so she can be longer at the bottom. 15min bottom time would require 40min of deco (on air), and is achievable with a SAC of 0.5ft3/min (and another cylinder near the surface, thinking of single Al80).

I hope I have been of help. Best of luck with your writing.

I find this a great help and would like to play with some options, if you don't mind. Storytelling/fiction gives room for creative license but I don't want to disgrace myself or the sport and the skill and experience of those of you who know better than I. However, I can take comfort knowing that the type of person that would know that this scenario isn't COMPLETELY realistic, will not be reading this novel. :blinking: Phew!

Addressing other comments: Yes, she can calm down and conserve air after her initial panic. No, she doesn't panic so bad she loses her reg. Yes she is weighted down, (darn jealous other woman competing for hero's affection). I know the dump valve issue is real, it happened to me. She can kick to slow herself down if that helps but she can't stop dropping because of the extra weight. She doesn't think to drop her weights and she is probably going to have a little narcosis at some point since she is not a party girl and not used to judgment impairment. (What does hero see in her then, right? ha ha)

I initially hoped for a longer than 3-5 min safety stop at 15-20 ft, but now wonder if I'll have to make the point of the scene without that. She can be out of air before hero reaches her but not for long. I could possibly have her go unconscious but not for long enough to drown or lose her reg. I can't kill her off.
Hero can either take an extra tank with him or people on boat can drop tank/tanks down as needed?? It is the timing--how long do I have before he has to notice she is gone, how far she can drop before hero notices, gears up, and gets to her, and brings her up. How many tanks would that take, without either of them dying or needing medical attention. That is what I need to hash out. If she would be out of air before 200ft, what is the farthest she could drop? And what is the most realistic, shortest amount of time she would have to be down to need an extra safety stop and if there are extra stops, what depths should they be and for how long? 15 mins would need a 40 min. stop? What if it was 8-10 mins? What max depth and how long then?


She starts to sink, panic, don't panic, blah, blah, blah. Hero notices, sees her bubbles, knows something is wrong, blah, blah, blah, throws on his fins and bc, grabs another tank or yells to captain, Drop a tank at _____ ft (fill in blank) Reaches her at ____ ft (fill in blank) Dumps her weights, takes her up, makes stop or stops for _____ mins (fill in blank)? Is that at least believable?
Get what I mean? What would you recommend? Thank you very much for your help.

---------- Post added October 29th, 2013 at 01:31 PM ----------

Ok, here goes my try.

Damsel is somewhat petit giving her a naturally low-ish SAC rate despite her being a newbie. She is diving an Al 80 tank with air. She is AOW (so that she is allowed in a Charter to dive a wreck like the Spiegel Grove) newbie with 12 dives under her belt. This is realistic because my instabuddy on my dive to the Spiegel Grove had this certification and experience level. Spiegel Grove sits in 130 ft of water but it is common for divers to stay at 80ft to 100ft for most of the dive.

Hero is diving double Al 80s because that is what he likes. He likes the balance. He just sets up his rig once for two boat dives. No exchanging of tanks during surface interval. And he likes the redundancy. This first dive of the day goes uneventful for 20 mins that Damsel spent at an average of 100 ft. Her computer says she's almost out of NDL time. So she starts to ascend. She saw Hero venting gas from his wing without breaking trim by pulling on the OPV valve. She gives it a try herself as she is ascending and hears a metallic snap following by rapid emptying of her BC and loss of bouyancy. She fell outside the wreck all the way to the 130 ft bottom.

About a year or 2 ago, several manufacturers (Halcyon, Dive Rite, Hog, etc) issued a recall on OPV valves that had a spring that could easily corrode and break. Damsel just happened to dive a BC with one such spring.

Damsel is starting to panic. This brings her normally lowish sac rate of 0.4 cu ft per min to 0.7 cu ft per min for the entire dive (including the non-emergency first 20 mins). Then she finally remembers that she can drop weights. Just as she is getting ready to drop weights Hero's steady hand comes over hers to prevent her from becoming a polaris missile to the surface. Overall Damsel spends a total of 5 additional minutes at 130ft.

Hero turns her body in a position where her bc holds air and starts taking her up. He checks her SPG and decides to put her on his long hose before she actually starts feeling an empty tank. He looks at his computer and SPG and makes some quick calculations. He pulls out a yellow SMB that has a little slate with a small pencil at the top. He writes "Send O2 for 2" and deploys the SMB while Damsel clings to his side (I know people who have had to write "Need O2" on a slate). He makes a 2 min stop at 40ft and another at 30ft. At 30ft a crewman from the boat joins them bringing 2 Al 40 tanks labelled Oxygen. At the 20 ft stop Hero grabs a regulator from an Al 40 and gives it to Damsel. Then Hero grabs one for himself. They do three mins at 20 ft and three more mins at 15 ft before they finally ascend.

Here's an applicable deco schedule with gas consumption figures:

MV-Plan 1.5.2
Settings: GF=30-80 Factors:1.0/1.0 ppH2O=2.041 ftsw ZHL16B
=========================================================
DESC: 99ft for 01:30 [ 2] on Air, SP: 0.0, END: 99ft
DIVE: 99ft for 18:30 [ 20] on Air, SP: 0.0, END: 99ft
DESC:130ft for 00:28 [ 20] on Air, SP: 0.0, END:130ft
DIVE:130ft for 05:00 [ 25] on Air, SP: 0.0, END:130ft
ASC : 50ft for 02:25 [ 28] on Air, SP: 0.0, END: 50ft
DECO: 50ft for 00:06 [ 28] on Air, SP: 0.0, END: 50ft M-Value: 63% [02], GF: 40%
DECO: 40ft for 02:00 [ 30] on Air, SP: 0.0, END: 40ft M-Value: 70% [02], GF: 50%
DECO: 30ft for 02:00 [ 32] on Air, SP: 0.0, END: 30ft M-Value: 75% [02], GF: 60%
DECO: 20ft for 03:00 [ 35] on Oxygen, SP: 0.0, END: 0ft M-Value: 81% [03], GF: 70%
DECO: 10ft for 03:00 [ 38] on Oxygen, SP: 0.0, END: 0ft M-Value: 83% [04], GF: 80%


Gas estimate based on Dive RMV =0.7, deco RMV =0.7cuft/min
Air : 85.5cuft
Oxygen : 6.1cuft
Oxygen Toxicity - OTUs: 29 CNS: 16%

That all sounds great. Can I quote you? Will you sign away any rights of ownership? ha ha

 

[Slamfire]

That all sounds great. Can I quote you? Will you sign away any rights of ownership? ha ha

I'd be honored to be quoted. I can sell you any rights of ownership for a signed copy of the book. Does it sound like a fair price?

 

[Sue-ba]

So I guess a Warhammer manoeuvre by the hero is out of the question during the deco stop even if he had a curry the night before

Sorry Sue I could not resist

Sorry, no Warhammer Maneuver in this scene ... but maybe the reason for it later??? :blinking:
You apparently are not familiar with the romance novel hero qualities. Nothing, even having curry the night before could diminish his glorious desirability and ability to pull off the Warhammer Maneuver, if he wanted to.

---------- Post added October 29th, 2013 at 01:44 PM ----------

I'd be honored to be quoted. I can sell you any rights of ownership for a signed copy of the book. Does it sound like a fair price?

Quite fair! But you might have to write the rest of the story for me too. Such a discrepancies between your words and my own would not go unnoticed. ha ha