Question Only Instructor wears dive computer (extra charge if I want one)

[BabyLitigator]

Yes the risk of dcs is never 0. But actual risk would mostly depend on the surface interval.

To rephrase. Standard double dip open water. Max depth of 60, max time of 45 (likely shorter with the type of folks that don’t own their own computer), 45 min surface interval.

Ran in V-planner and got 20 seconds of deco on the second dive assuming all 90 minutes are at 60 feet and not shallower.

FWIW my last ‘trust me’ dive (cruise ship, Cabo) I don’t think gave out computers but based on my computer was miles away from a likely dcs issue (or at least a computer warning of one).

 

[Belzelbub]

To rephrase. Standard double dip open water. Max depth of 60, max time of 45 (likely shorter with the type of folks that don’t own their own computer), 45 min surface interval.

Ran in V-planner and got 20 seconds of deco on the second dive assuming all 90 minutes are at 60 feet and not shallower.

Ok. And? You take the risks you are comfortable with. A safety stop is a good idea, but can be skipped if circumstances dictate otherwise.

V-Planner and dive computers run on theoretical models. None actually tell you what is actually going on with your tissues. Your actual rate of on-gassing and off-gassing will vary from person to person and day to day.

 

[Dan G]

Yes those are rather moderate dive profiles, but being prepared for things to go not as planned is a good idea. For example, going deeper than the DM by mistake. Computers also help with a proper ascent rate and the SS. To me PDC is just standard dive equipment and an item I tell people to get when they ask which piece of diving equipment they should get first.

 

[MB NZ]

Haven't read the whole thread, but everyone should have their own computer and learn how to use it.

Anecdote: My wife and I did a guided dive in the Cook Islands. Easy, holiday diving. Dive guide spent most of the dive at 30 metres. As the NDL ticked down, we came up to 20 metres while the guide and other customers stayed at 30 metres. We followed them from above. Dive ended and everyone survived as far as I know, but it transpired that the guide had his computer set to nitrox and we were all diving air. Not ideal.

 

[lowwall]

With a one day double dip within open water limits (60 ft) and 45 minute dive, is it really possible to get into nitrogen trouble?

With a reasonable surface interval, you wouldn't exceed the NDL for any computer on its standard settings.

However... [Pet peeve alert]. 60' is not the open water limit (unless you are 12-14 years old). The actual limit for OW divers under WRSTC standards (which covers all the standard for profit agencies) is 40m/130’. The 60' limit only applies to training dives before certification:

5.2.3 All dives prior to open water certification shall be conducted during daylight hours* at depths between 15 and 60 feet (5 to 18 metres).

Some dive operators may choose to enforce a 60' limit on guided dives for insurance or other reasons, but it has never been a certification requirement.

 

[Thunder Struck]

Yes those are rather moderate dive profiles, but being prepared for things to go not as planned is a good idea. For example, going deeper than the DM by mistake. Computers also help with a proper ascent rate and the SS. To me PDC is just standard dive equipment and an item I tell people to get when they ask which piece of diving equipment they should get first.

With used computers being so affordable compared to the rest of the cost of a trip it’s hard to argue why not have one. Sure it may not be the latest Shearatiomin Perdescentric with Bluetooth LE syncing to your phone, but it’ll do what is needed if someone doesn’t want to run tables.

Otherwise one of the first pieces of gear I recommend is a small dive light for peeking into the cracks and crevices to see all the cool fishies you went there to see in the first place. Hell, a dive light can easily cost more than a basic used puck computer.

 

[Nick_Radov]

Even if the dive profile is very regimented from a depth and time standpoint, this is really a no-no in the modern era of diving. Modern computers take into account your depth, air usage and time in a way that is very precise from a Nitrogen loading standpoint.

A dive computer will give you very precise output. That doesn't necessarily mean it is accurate in the sense of correctly modeling what's happening in your body. Many divers fail to understand that precision and accuracy are separate mathematical concepts.

It's generally helpful (although not required) to bring a computer. Just don't put blind trust in what it tells you.

 

[NothingClever]

…finished my advanced Open Water Diver in December.
…and I wondered…If I’ll be fine without a computer

Well, I don’t want your first brush with SB to be an acerbic one but the above question leaves me scratching my head a bit about the quality of your Basic and Advanced OW instructors. I think they let you down, to be honest.

Invest in yourself - get a computer.

 

[Derbdiver]

To rephrase. Standard double dip open water. Max depth of 60, max time of 45 (likely shorter with the type of folks that don’t own their own computer), 45 min surface interval.

Ran in V-planner and got 20 seconds of deco on the second dive assuming all 90 minutes are at 60 feet and not shallower.

FWIW my last ‘trust me’ dive (cruise ship, Cabo) I don’t think gave out computers but based on my computer was miles away from a likely dcs issue (or at least a computer warning of one).

So, if you are diving from tables you always make your deepest dive first. It is general practice to dive to a shallower depth on each successive dive. Dive tables are very gross approximations of your pressure group. In order to properly answer your question a lot of it has to do with physiology, how fast you consume your air and then depth and time at depth. This link is very technical but it does talk about Physiology of the Diver and how that changes the Nitrogen absorbed. Computers keep things conservative but they also do a much better job of tracking time at depth and you will always increase your total dive time by using a computer. https://journals.physiology.org/doi/full/10.1152/japplphysiol.91104.2008

 

[Derbdiver]

Well, I don’t want your first brush with SB to be an acerbic one but the above question leaves me scratching my head a bit about the quality of your Basic and Advanced OW instructors. I think they let you down, to be honest.

Invest in yourself - get a computer.

Totally agree, on that note I haven't purchased a computer for a number of years but this is one area where it seems the pricing has not gone up as drastically as everything else: Dive Computers | Divers Supply. Air integrated is ideal but $165 for a wrist unit your first dozen dives is much better than Dive Tables.