Is a Computer essential kit?

[Celt]

My first dives in Cozumel were multilevel dives well beyond the limits of dive tables.

I have dived to a maximum depth of 100 feet with a bottom time of well over 80 minutes, all within NDLs.

Here is a 3-tank dive I did on 5/17/2018:

1. 96 feet for 48 minutes
roughly 1 hour surface interval

2. 78 feet for 68 minutes
roughly 90 minute surface interval

3. 99 feet for 59 minutes.

You were not at those depths for those bottom time without deco, Even if I was on 40% EAN I would have 10 min deco on the last dive.
95ft/48 minutes
1 hour surface interval
80ft/68 minutes
1 hour surface interval
100ft/60 minutes deco 10min at 10 feet.
There’s no dive that can’t be preplanned and carried out. The OP can make the dives he asked about in complete safety without carrying a computer and it’s very poor advise from some to say otherwise. He may wish to use a computer and enjoy it but absolutely not essential.

 

[rongoodman]

I think planning dives and calculating pressure groups for repetitive dives is an essential skill.

Why? Depth, time, surface interval, and gas used all are relevant to dive planning, whether with a PDC, deco software, or dive tables, but pressure groups have no meaning outside the particular dive tables they're used with.

 

[rongoodman]

You need a Shearwater.



Is that Scubaboard enough of an answer?
(no you don't need one.)

No, but many here think you'd be better off with a PDC running a known algorithm which will not lock you out. Shearwater just happens to be the most popular example put forward on Scubaboard recently.

 

[Celt]

My advice to the OP is don’t bother with a computer for the moment. Get some diving done. Go out to the sites you plan on diving and bring a pen and paper ( it’s cheap) take notes on the landscape at high and low water. Find good entry and exits. Often with shore sites the geology close to the shore extends out into the water. Check with the locals or fishermen. Keep a record of your diving. Prevailing wind direction , underwater structures and nice leads in and out. A bit of time spent studying beats throwing money away every time.

 

[jonhall]

G'day, just wanting a broader range of opinions rather than those who will profit from selling me a computer.

Just to jump in the fray... The advice on computers is good and I agree, but if you know your type of diving will be what you described or if you're asking about this 1 specific weekend, then no, you don't need a computer....even though many of the comments read as if they're trying to sell you on the idea you should get a computer and why.

Several comments have mentioned that a computer will extend your dive time, but for what you described, a computer will not magically make your 1st dive or 2nd dive of the day longer - I often joke on the golf course about emails I get that say I can take strokes off of my game with a new rangefinder, new shoes, a new club, etc... - doesn't happen!

If you're doing what might be considered a 'normal' day of diving - 2 dives from a boat, multiple dives from a live aboard, dives in the morning and later in the day, all at various depths or multiple days of 'normal' diving - then having a computer do all of the work for you (giving you more time that you can safely stay down, seeing your NDL, seeing how long a surface interval should be) makes sense. For what you described, you're going to dive the air you have in your tank however long it or your dive lasts; take a long, more than what the tables would recommend, break; and then dive another tank however long it or your dive lasts. You don't even need tables.

If you plan to expand your type of diving, then yes, at some point you should consider a dive computer. There are more expert divers here on SB to give you advice, but my suggestion is research and find a computer with a generous algorithm, which can magically add minutes to your safe diving time.

 

[arew+4]

@boulderjohn

I say essential because it helps to solidify the basics of decompression theory for new divers. Also, I'm not fan of blindly trusting technology, I use it all the time but I always try to understand the inner workings at a rudimentary level.

 

[NothingClever]

In the spirit of refraining from using technological conveniences, I offer, lightheartedly mind you, the following tips to ensure a consistent experience.

#1 - Take some regular work gloves, not dive gloves, as paying out and retrieving the knotted line to take soundings will wear out your neoprene dive gloves. Those electronic depthfinders are unnecessary to find the wreck.

#2 - Make sure to take your sextant readings from amidships since the boat rocks the least there and your sighting accuracy will be better. That silly GPS is superfluous.

#3 - Bring along extra pine pitch or animal fat in your save-a-dive kit. Salt water is corrosive to any sewn seams on your goat skin air bladders. Aluminum and steel tanks are for the weak.

#4 - Double up on the gloves if doing a three tank (err, bladder) dive. They’ll save your hands as you row your way to the dive site. Internal combustion engines are for the faint of heart and real divers don’t need them.

Smile everyone.

 

[boulderjohn]

You were not at those depths for those bottom time without deco, Even if I was on 40% EAN I would have 10 min deco on the last dive.
95ft/48 minutes
1 hour surface interval
80ft/68 minutes
1 hour surface interval
100ft/60 minutes deco 10min at 10 feet.
There’s no dive that can’t be preplanned and carried out. The OP can make the dives he asked about in complete safety without carrying a computer and it’s very poor advise from some to say otherwise. He may wish to use a computer and enjoy it but absolutely not essential.

You said:

What I’d like to know is what dive can not be made without a computer.

Name the dive area and depth and I’ll explain how to dive it .

Well, I named dives that you apparently think cannot be made without a computer. Those divers were not near NDLs. Dives that are not at the same depth the entire time are called multi-level dives. If you look up the phrase, you can learn all about them,

 

[boulderjohn]

@boulderjohn

I say essential because it helps to solidify the basics of decompression theory for new divers. Also, I'm not fan of blindly trusting technology, I use it all the time but I always try to understand the inner workings at a rudimentary level.

"Essential" and "helps" are not the same concept.

I taught OW diving to new divers for years. I taught them decompression theory. Then I taught them how to deal with decompression when they dived. For the first years that I taught that, I showed them how to use tables for that purpose. For the rest of the years, I taught them how to use computers to do that.

Many people learned decompression theory and tables at the same time and mistakenly believe you cannot teach one without the other. Mark Powell wrote and an entire book on decompression theory (Deco for Divers) and never wrote a single sentence teaching how to use tables.

EDIT: My most recent tech student has a pretty darn good idea of decompression theory, and he can plan decompression dives. He never learned how to use tables (other than the software version on SubSurface).

 

[Celt]

Well, I named dives that you apparently think cannot be made without a computer. Those divers were not near NDLs. Dives that are not at the same depth the entire time are called multi-level dives. If you look up the phrase, you can learn all about them,

It’s the opposite. I know they can be made without a computer. We were making so called multi level no deco dives 40 years ago using a 120 rule long before computer users claimed it like it was some kind of a revelation. A watch and simple arithmetic which seems to be beyond today’s diver who have been dumbed down by so called technology