Wisdom of trusting one's dive computer?

[CaveSloth]

I have a Shearwater Teric. I pay attention to the NDL reading and I ascend any time it gets too low. According to the computer I have never incurred a deco obligation and I also have never been bent over the course of 67 dives.

I recently dived with a buddy who is into the GUE approach, and he said that he only dives with his computer in gauge mode and always calculates his dive plan in advance to avoid deco or account for it or whatever.

What is the better approach? Trusting the computer or doing pre-dive planning?

The lame thing about the pre-planning is it doesn't really leave any freedom. With the computer, it feels like I am safe to dive without any plan whatsoever, other than making sure not to incur deco.

If I have my computer set to conservative settings and it is a trusted brand and algorithm, aren't I safe to trust what it says?

 

[Dubious]

With the computer, it feels like I am safe to dive without any plan whatsoever, other than making sure not to incur deco.

I think here lies the concern. I was taught to always plan the dive and dive the plan. The computer is just a tool for that.

 

[FreeFlyFreak]

Personally with my Petrel I dive following the algorithm with conservativism @ 85 for warm water, and 75 for cold.

 

[CaveSloth]

I think here lies the concern. I was taught to always plan the dive and dive the plan. The computer is just a tool for that.

But how can you know what the plan is when you don't know how long it will take you to explore any particular area? You may get bored and decide to go to the next area, or linger in a particular area. Or, you may get stuck in one area or current may propel you quickly through another area. The computer adapts to that kind of thing perfectly.

 

[Manatee Diver]

The GUE has their own way of doing things. Is it the right way of doing it? I don't know, it seems to work for them, but it isn't how I would want to dive.

 

[doctormike]

Ideally, you should have enough understanding of what deco is and how much time you have at your maximum depth to know if something is very off with what your computer is telling you. That having been said, the main reason why people dive computers is that they give you "credit" for time spent above your maximum depth.

Planning a dive ahead of time and sticking to that plan means either diving a square profile or doing a shorter run time than necessary to avoid DCS for a given set of dive parameters.

The computer knows what you actually did on the dive in real time. If working and programmed correctly, it will be constantly calculating your nitrogen loading and letting you know how much time you have left at any given depth before incurring a deco obligation (i.e. NDLs).

As a practical matter, in 2019 the vast majority of recreational divers watch their dive computers and their SPGs, and ascend when they either run out of NDL or hit their minimum ascent pressure, whichever comes first.

 

[lexvil]

Find a new buddy or dive his way while you dive with him, I would concentrate on the former.
There are times when good planing is essential.

 

[doctormike]

I think that planning is important, even for recreational divers. The main thing about tech training isn't gear or procedures, it's mindset. It's the difference between just swimming around and watching your SPG and computer, and planning a dive. Divers at all levels can benefit from that.

That having been said, as long as you have planned the dive and are in a non-overhead environment (physical or virtual), there is nothing wrong with changing that plan on the fly to involve LESS nitrogen loading and/or gas consumption, and then just watching your instruments.

 

[NAM001]

I know I will get hit for this but you are doing rec diving and not tech diving, the GUE process is not really tuned to our rec diving needs. As mentioned the GUE guy says he computes his plan to avoid deco. The computer does that for you. the real meat of the matter is if the computer fails or is lost from a broke strap or something what do you do. The GUE divers like most tech divers used a one process fits all situations, If it is good for a 200 ft dive its good for a 70 ft dive. they learn the skill for deep deco dives. Until you start doing those dives I would stick to the computer in normal mode. Unless you are willing and proficient in calculating deco if you stay too long then stick to the computer in normal mode. This is a long time argument with tech divers and rec divers. their processes though well though out , bare not for the dives you do not do. If you stay a minute too long it is a cake walk to handle in < 100 foot dives. 200 ft dives have an entirely different consequence to a couple minute overstay at depth. They use a different set of tools like ratio deco to calculate the deco proceedure for their TECH dive.

 

[NAM001]

But how can you know what the plan is when you don't know how long it will take you to explore any particular area? You may get bored and decide to go to the next area, or linger in a particular area. Or, you may get stuck in one area or current may propel you quickly through another area. The computer adapts to that kind of thing perfectly.

I invite you to do some reading on ratio deco. That system requires only a depth gage and timer. You will probably quickly see it is not for you when you attempt to apply it to rec diving. RATIO DECO IS DECO PLANNING....... REC DIVING IS NON DECO DIVING.