Tec Diving Journey / Seeking Advice

[SelfDiver]

You had Yosemite Sam as your IT, huh?

He said ooga booga and grunted

 

[jadairiii]

Ah. I should have clarified. Across the dives I was in the range of 22 - 28% O2 - depending on the depth. Deco was 50% on a few and 80% O2 on the last one.

22-28% = Air

80%, just say no. Use O2.

If you find a Tech instructor who teaches deep air or 80%, its a good indication you need a different instructor. Sort of like meeting your airline pilot before takeoff at the airport bar.....take another flight.

 

[NothingClever]

@hammerhead_sm is diving in India. I’m betting the dive shops don’t have a booster to fill cylinders with 100% to full operating pressure. They transfill O2 into the receiving cylinder and then use air to get to the desired pressure. I had to settle for 80% in Saudi Arabia because there simply wasn’t anything else available.

 

[LanceRiley]

I suggest take up a class. Like Gue Fundamentals.

 

[Nick_Radov]

@hammerhead_sm is diving in India. I’m betting the dive shops don’t have a booster to fill cylinders with 100% to full operating pressure. They transfill O2 into the receiving cylinder and then use air to get to the desired pressure. I had to settle for 80% in Saudi Arabia because there simply wasn’t anything else available.

Instead of compromising with the wrong mix, just use a larger deco stage tank and run lower pressures. The bounce dive profiles that we're discussing here don't require a huge volume of O2 anyway.

 

[ToneNQ]

As you've seen, GUE Fundies is the oft recommended answer when people have little else to contribute. GUE is a miniscule community, especially outside the USA. I will agree the GUE divers that I have dived with are impeccable in the water, but their dive planning and decompression theory wasn't inspiring. GUE divers go to trimix gas blends quite early, most buy Helium at USA prices or they spend a fortune. A mate of mine spent AU$1400 on gas for a weekend of GUE diving on GUE standard mixes. He left Sydney a few years back and lost his cert for not doing his (?25 per year?) dives with GUE groups using GUE blends, even though there was no GUE presence where he now lives. In regional areas its just not viable, but it is certainly held in high regard by those inside the GUE community.

As an AN/DP diver you've got a ways to go before you can add Helium. You can do Helitrox to breathe hyperoxic mixes, but the dives you are doing are not deep air. Trimix breathes lighter, much easier at depth and you'll shed CO2 better. Its a good call to use it if you're qualified, but it is expensive. If you go somewhere like Bikini Atoll, only CCR gets Trimix as they cannot carry enough Helium. OC divers all use air at 52m max depth and they're fine. Just cruise, don't work yourself hard and stay on top of your breathing rate. If Trimix 75 is your goal, get the eLearning and start the process. Trimix is an awesome course, just watch out for the gas bill at the end.

Holding depth on deco has a lot of feel to it. A lot of tech divers dive regularly, many of us dive when we can. The first few dives take a bit to get the feel back, always do a shakeout dive first and go easy on yourself. Put up a DSMB and hold it out at arms' length so you get a feel for the changes, then close your eyes and try to feel it with your ear pressure, your arm angle, etc. Its 1000% easier to maintain depth in horizontal trim so work on that. Give yourself time, patience, and hours in the water. Guys that do 400 dives are year are superb. Guys that do 25 tend to look amateurish.

As to some of the other advice here, you have to work within your cert level what gases you can get locally. Deco on EAN 50 works fine for 40m dives. EAN 80 is better. Carrying 100% O2 is really only practical when you level-up to carrying two deco tanks on your next tech course. As an exercise, check your dive plans with a few different deco mixes. For all the waffle about 80% being a stroke mix, the difference from 100% is a few minutes. In some locations the absolute best O2 mix you'll get is 92% and again, the difference is a minute or two.

 

[Nick_Radov]

As you've seen, GUE Fundies is the oft recommended answer when people have little else to contribute.

It's the oft recommended answer because it works, and avoids rehashing topics that have been covered multiple times before.

GUE is a miniscule community, especially outside the USA. I will agree the GUE divers that I have dived with are impeccable in the water, but their dive planning and decompression theory wasn't inspiring.

Be more specific instead of wasting everyone's time with vague innuendo. What specifically "wasn't inspiring"? Was something specifically wrong, or just different? Only the upper level GUE courses get into really detailed dive planning and decompression theory.

GUE divers go to trimix gas blends quite early, most buy Helium at USA prices or they spend a fortune. A mate of mine spent AU$1400 on gas for a weekend of GUE diving on GUE standard mixes.

Yes, helium is expensive. So what. If you can't afford to use the correct gas then don't do the dive. There's plenty to see shallower than 30m.

He left Sydney a few years back and lost his cert for not doing his (?25 per year?) dives with GUE groups using GUE blends, even though there was no GUE presence where he now lives.

GUE certification renewal only requires 8 dives per year. There is no requirement that those dives be "with GUE groups using GUE blends" (although it's always best to dive with teammates who have similar training, and standard gasses usually make logistics easier). Instead of relying on secondhand statements it's best to check your facts from reliable sources.

As an AN/DP diver you've got a ways to go before you can add Helium. You can do Helitrox to breathe hyperoxic mixes, but the dives you are doing are not deep air. Trimix breathes lighter, much easier at depth and you'll shed CO2 better. Its a good call to use it if you're qualified, but it is expensive. If you go somewhere like Bikini Atoll, only CCR gets Trimix as they cannot carry enough Helium. OC divers all use air at 52m max depth and they're fine.

They're not "fine". This is stupid, terrible advice. Feel free to take the risk of diving deep air if you want but this is not what we should be recommending to new tech divers who need all of the safety margin they can get. For @hammerhead_sm , you should search here for "deep air" and spend some time understanding all of the concerns with using air (or nitrox) deeper than about 30m. This has been discussed ad nauseam in multiple thread going back years so there's no need to repeat it all here.

Holding depth on deco has a lot of feel to it. A lot of tech divers dive regularly, many of us dive when we can. The first few dives take a bit to get the feel back, always do a shakeout dive first and go easy on yourself. Put up a DSMB and hold it out at arms' length so you get a feel for the changes, then close your eyes and try to feel it with your ear pressure, your arm angle, etc. Its 1000% easier to maintain depth in horizontal trim so work on that. Give yourself time, patience, and hours in the water. Guys that do 400 dives are year are superb. Guys that do 25 tend to look amateurish.

This is actually excellent advice.

As to some of the other advice here, you have to work within your cert level what gases you can get locally. Deco on EAN 50 works fine for 40m dives. EAN 80 is better.

For a typical dive to 40m with a single deco gas it's usually best to use EAN 50. Regardless of theoretical deco time calculations of EAN 50 versus 80 (or something else), the larger concern is contingency planning. If you have a problem with your bottom gas then you can ascend directly to 21m and immediately switch to EAN 50 rather than waiting until you reach 9m where it's safe to switch to EAN 80 (which might require first doing some deeper deco stops on back gas depending on bottom time).

Carrying 100% O2 is really only practical when you level-up to carrying two deco tanks on your next tech course.

I generally agree with that. There is a huge difference in the risk of a gas switching error between one versus multiple deco gasses, so get some training and experience using a single deco gas first (regardless of specific mix). But there are scenarios where carrying 100% O2 as your single deco gas makes sense. We sometimes do really long but relatively shallow dives where we have a significant deco obligation at 6m or less, so for those dives O2 is the optimal choice.

As an exercise, check your dive plans with a few different deco mixes. For all the waffle about 80% being a stroke mix, the difference from 100% is a few minutes. In some locations the absolute best O2 mix you'll get is 92% and again, the difference is a minute or two.

Here we go again. In real tech diving there are multiple concerns with gas planning beyond just deco time. For reference here is the (in)famous "Baker's Dozen" post from 1997; the "oxygen window" part appears to be based on a misunderstanding of gas laws but the other reasons are still valid.

I don't know what locations you're referring to, but you can get 100% O2 pretty much anywhere that tech diving is possible. It might not be available at the pressure you want if they lack a booster. In that case the solution is not to goof around with a ridiculous mix but rather bring a larger deco stage tank and run a lower pressure. Unless you're a total hoover you can get a lot of time at 6m or less out of even a little Al40 stage filled to ⅔ of rated pressure. This is not an actual problem.

 

[ToneNQ]

.....snip

Be more specific instead of wasting everyone's time with vague innuendo. What specifically "wasn't inspiring"? Was something specifically wrong, or just different? Only the upper level GUE courses get into really detailed dive planning and decompression theory.

Yes, helium is expensive. So what. If you can't afford to use the correct gas then don't do the dive. There's plenty to see shallower than 30m.

GUE certification renewal only requires 8 dives per year. There is no requirement that those dives be "with GUE groups using GUE blends" (although it's always best to dive with teammates who have similar training, and standard gasses usually make logistics easier). Instead of relying on secondhand statements it's best to check your facts from reliable sources.

snip....

No, the vague innuendo is simply that doing Fundies will solve the issues of an Indian-based diver. Are there any GUE instructors in India? Should he fly back to Thailand to do Fundies? Or should he just practice locally and maybe we give him some actual advice on skills he can use to get better? Did you learn a skill on Fundies that the OP could use? Share that, be helpful.

Have you ever had someone explain ratio decompression to you and not found it uninspiring? Why the GF Low of 20 is the default value and how that doesn't align with Doppler evidence? The oxygen window and spending longer deeper for the higher PPO2 rather than increasing time on the 12 and 9m stops? You guys are impeccable in the water, I'll give you that. I'm not being inflammatory, just arguing some of the points made in this thread. I'm glad you acknowledge the oxygen window, but the Baker's dozen is based on 100% being available and a diver certified for multiple deco tanks. For the OP as a single deco tank certified diver, its not an option. 1 is full of hubris, 2 is not valid to single deco tank diving, neither is 3, 4 doesn't apply to the OP, 5 is worthless as its totally wedded to the oxygen window, 6 doesn't matter for the OP, 7 is total hubris, 8 is all about the O2 window, 9 is hubris, 10 is not relevant to the OP, 11 not relevant, 12 is sheer hubris, 13 is being a pompous ass. Again, we give advice for the OP based on the OP. I'd carry EAN50, have done many times. If that tank got low and the boat had a tank of EAN70 or 80, I'd dive it without a second thought. The gas switch is now at 9m, but for a 40m dive the first stop is usually at 9m anyway if using a GF Low of 50. Maybe it's 12m for the second dive, but as a deco mix its fine and the Baker's Dozen does nothing to undermine the maths. In 2025 it's ideological, any basis in diving physiology is long discredited.

The correct gas is one that has a density of 5.2 g/L, and no greater than 6.2 g/L. What evidence exists that a GUE standard mix is the 'correct gas' and that diving within the guidelines of other agencies is high risk? As for plenty to see shallower than 30m, your diving world is minuscule. Most wrecks sit from 35 to 65m and many of these can be dived safely on air. Not a great idea on a CCR with the higher loop resistance, but on OC its a personal decision based on your narcotic tendencies and your ideal END. I find 20/20 diluent is great on 50m dives, so why pay 30c/L for Helium just because the standard mix says 21/35 or 18/45? That you argue you can get 100% O2 everywhere is hilarious, oh my sweet summer child. And its still not relevant for the OP who clearly states he is an AN/DP diver. But hey, call me out for wasting everyone's time.

As for the precise quantity of dives for GUE recertification, there are question marks in my comment for a reason. I can't recall exactly how many dives he said he needed, but he had more than enough. I can clearly recall what he told me about why he lost his T2 cert. It won't matter if the reason he got was fair or otherwise because he's been burned badly by the experience and if it turns out to be the instructor's whim, that only makes it worse. He had done plenty of trimix diving, the quantity alone was enough. Final point; what I got was a first-hand statement, what I gave was a second-hand statement. You could not testify in court with my statement, that would be heresay, but I could.



Getting back to the OP, fins, if your feet a light consider two things. The Go Sport fins are positive, what boots are you wearing? If they're a standard 5mm boot, maybe look at 3mm shoes like the Fourth Element Rock Hopper to reduce the positive bouyancy of your feet. You can get heavier fins, I have Jet fins but the foot pocket is wrong for my high arches. I wear Fourth Element tech fins when diving dry but they're too heavy to travel with. I just got a pair of Go Sport Gorilla fins for travel and bought the rock hopper shoes as well, untested for now but I'm diving next weekend and testing them. I've also got a few pairs of Cressi fins, but they're too long for wreck diving.

Regarding your sideways balance in trim, how tight do you wear your backplate? Check your shoulder straps are even, not pulling the rig to one side. Consider loosening the shoulder straps a touch, maybe 2cm but go by your feel, keep the waist belt tight and low on your hips. Then once your at depth, you can wriggle around under your twinset. I like to have a little wriggle room, just get it into the exact spot that is comfortable

 

[Nick_Radov]

No, the vague innuendo is simply that doing Fundies will solve the issues of an Indian-based diver.

That is a disingenuous strawman argument. No one claimed that a single short course like GUE Technical Fundamentals can completely "solve the issues" that @hammerhead_sm described. But it would be a great first step in a longer journey.

Are there any GUE instructors in India? Should he fly back to Thailand to do Fundies?

Sure, why not? Many divers (including me) have travelled, even internationally, for training classes. Alternatively, many GUE instructors are willing to come to you if you pay their expenses so that can be a better option if you have some local friends to share the cost.

Or should he just practice locally and maybe we give him some actual advice on skills he can use to get better? Did you learn a skill on Fundies that the OP could use? Share that, be helpful.

I learned many skills related to trim, propulsion, failure management, emergency procedures, equipment configuration, team coordination, and dive planning. But the Technical Fundamentals course now is substantially different from when I took Fundamentals back in 2001 (when it wasn't a certification course) so I would recommend that OP refer to the official description and more recent student reports.

Have you ever had someone explain ratio decompression to you and not found it uninspiring? Why the GF Low of 20 is the default value and how that doesn't align with Doppler evidence? The oxygen window and spending longer deeper for the higher PPO2 rather than increasing time on the 12 and 9m stops? You guys are impeccable in the water, I'll give you that. I'm not being inflammatory, just arguing some of the points made in this thread.

I can't imagine why you would think that ratio deco should be inspiring? You totally missed the point. There's nothing magic about ratio deco. It's simply a recognition that a 3D surface (the relationship between depth and bottom time versus total deco time) can be approximated within a limited area by a tangent plane, and a 2D curve (the deco ceiling) can be approximated with a series of straight line segments. This is trivially true and just basic high school level math. Feel free to use any gradient factors or deco model that make you happy, it doesn't matter. You can work out your own ratios to match any model within reasonable constraints.
Ratio deco was developed primarily as a tool to develop thinking divers who could adjust plans on the fly without being dependent on deco planning software. It's somewhat less relevant now than it was 20 years ago given the current widespread availability of smartphone apps and dive computers with planning modes. But it's still useful to develop an intuitive sense of deco models so that you can estimate the impact of minor changes to your dive plan on deco profiles and gas consumption.

I'm glad you acknowledge the oxygen window, but the Baker's dozen is based on 100% being available and a diver certified for multiple deco tanks. For the OP as a single deco tank certified diver, its not an option. 1 is full of hubris, 2 is not valid to single deco tank diving, neither is 3, 4 doesn't apply to the OP, 5 is worthless as its totally wedded to the oxygen window, 6 doesn't matter for the OP, 7 is total hubris, 8 is all about the O2 window, 9 is hubris, 10 is not relevant to the OP, 11 not relevant, 12 is sheer hubris, 13 is being a pompous ass. Again, we give advice for the OP based on the OP. I'd carry EAN50, have done many times. If that tank got low and the boat had a tank of EAN70 or 80, I'd dive it without a second thought.

Why are we diving on boats that supply bizarre mixes in the first place? How are we marking that deco stage? You're not making any sense. This is why we have Rule #1 and Option #1.

If the boat has EAN 70 available then obviously they're doing partial pressure mixing. Which means they must have 100% O2 supply cylinders available, so you can fill a deco stage with 100% O2 to whatever pressure is available.

The gas switch is now at 9m, but for a 40m dive the first stop is usually at 9m anyway if using a GF Low of 50. Maybe it's 12m for the second dive, but as a deco mix its fine and the Baker's Dozen does nothing to undermine the maths. In 2025 it's ideological, any basis in diving physiology is long discredited.

Again you appear to have totally missed the main point of the "Baker's Dozen" post in that there are practical concerns which go beyond theoretical deco time.

The correct gas is one that has a density of 5.2 g/L, and no greater than 6.2 g/L. What evidence exists that a GUE standard mix is the 'correct gas' and that diving within the guidelines of other agencies is high risk?

I don't know what you mean by "correct". GUE standard open circuit mixes are based on a maximum END, maximum density, and maximum PO2. You can always add more helium if you like. While sticking to the standard mixes makes things simpler, safer, and easier in most circumstances there are no GUE police to punish you if you use a different mix outside of a training course.

As for plenty to see shallower than 30m, your diving world is minuscule.

Thanks but I've been diving all over the world. Never had a chance to dive in India yet, but based on some spectacular underwater photos from shallow sites there's apparently plenty to see.

Most wrecks sit from 35 to 65m and many of these can be dived safely on air. Not a great idea on a CCR with the higher loop resistance, but on OC its a personal decision based on your narcotic tendencies and your ideal END. I find 20/20 diluent is great on 50m dives, so why pay 30c/L for Helium just because the standard mix says 21/35 or 18/45? That you argue you can get 100% O2 everywhere is hilarious, oh my sweet summer child.

Personally I'm not willing to risk my life on deep air just to see another pile of rust. If they're doing partial pressure gas mixing then there is 100% O2 available.

As for the precise quantity of dives for GUE recertification, there are question marks in my comment for a reason. I can't recall exactly how many dives he said he needed, but he had more than enough. I can clearly recall what he told me about why he lost his T2 cert. It won't matter if the reason he got was fair or otherwise because he's been burned badly by the experience and if it turns out to be the instructor's whim, that only makes it worse. He had done plenty of trimix diving, the quantity alone was enough. Final point; what I got was a first-hand statement, what I gave was a second-hand statement. You could not testify in court with my statement, that would be heresay, but I could.

You either misunderstood what your friend told you, or he didn't give you the whole story. The GUE Certification Renewal process only requires a signed statement that you have met the minimum dive requirements and a $30 processing fee. They don't even ask about teammates or gas selection or anything like that. If your certification has already lapsed then you might also have to submit a copy of your dive log as evidence. That's it. Instructors aren't a factor. In theory I suppose GUE could revoke a certification for something really egregious but I've never heard of that happening.

Frankly I don't believe you. This is why it's unwise to rely on vague secondhand information. If you want to know the real deal then contact GUE directly and ask; they have always been willing to answer my questions.

 

[nadwidny]

. Most wrecks sit from 35 to 65m and many of these can be dived safely on air.

No they can't. Deep air is stupid.