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[Dive computer] buying advice

Discussion in 'New Divers and Those Considering Diving' started by Nodeist, Jan 10, 2017.

  1. scubadada

    scubadada Diver Staff Member ScubaBoard Supporter

    # of Dives: 1,000 - 2,499
    Location: Philadelphia and Boynton Beach
    Hi Diving Dubai,

    I'm no expert on cold water diving, hopefully, others will help us. I had about 150 dives in Southern California between 1970 and 1980 in a custom 1/4 inch wet suit. We dived USN tables. I have about 50 contemporary dives, mostly in San Diego with temps between high 40s and mid 50s in a full 7 mm and hooded vest. I have always dived my Oceanic computers running DSAT, no adjustment. I dive the same as I do in Florida or other warm water, often pushing NDLs and occasionally doing light deco. I'm also very interested in hearing what others have to say

    Good diving, Craig
  2. stuartv

    stuartv Seeking the Light ScubaBoard Supporter

    # of Dives: 200 - 499
    Location: Manassas, VA
    Like @scubadada said, typical boat where? In NC and NJ, the boats I've been on do a dive, an SI where people may eat something if they brought it, a second dive, and then head back in. If both dives are on the same site, the SI could easily be "encouraged" to be 45 minutes. Even if the boat moves to a new site for the second dive, the sites seem to be normally chosen so that the boat is at the second site and ready for divers to enter after a 1 hour surface interval. It is also common to hear the boat captain start to tell people "okay, folks, it's been an hour," meaning they have had a 1 hour surface internal, so they should be getting in again, if they want to do a second dive.

    People frequently eat their lunch after the second dive, on the 1 - 2 hour ride back into the dock. Those boats don't usually go out for afternoon dives.

    I did SDI OW, which really just focused on using computers for diving. I do not recall anything about using tables and picking the next depth level for determining NDL in cold water. I also do not recall anything specifically said along the lines of "if you're diving in cold water, bump up your computer's conservatism."

    So, in my very limited experience, I'd say the answer to your specific question is no, that doesn't seem to be normal practice.

    And, I do not know how people handle cold water diving, in this regard. I believe tech divers will generally use lower GF numbers. But, I really don't know what, if anything, "typical" rec divers do in this regard. I have never talked to any of them regarding that subject. However, my suspicion would be that those recreational divers diving in cold water do not make any adjustments to their computer based on it being cold water. I suspect they either dive in the cold for as they long as they can stand it, or as long as their gas holds out, and if all that is as long as their NDL, then they just dive their NDL.

    I haven't done a comprehensive survey, but the only computers I can think of that take temperature into account are the ScubaPro ones with their biometric factors that they incorporate. I think they claim to factor in water temp, skin temp, heart rate, and gas consumption. I would GUESS that they would only use those factors to shorten NDLs, never lengthen them. But, I guess that information is proprietary and it's moot for me as I won't be using one of those computers in the foreseeable future.

    The only published, peer-reviewed deco algorithms that I know of - at least, that are in use in commercially available computers - do not include any kind of temperature in their parameters. I'll be sticking to computers with those kind of algorithms in the foreseeable future and managing my own conservatism parameters.
  3. dmaziuk

    dmaziuk Regular of the Pub

    Right. A ferry to Rottnest from Fremantle Western Australia is about 90 minutes, a dive boat will probably need more like 2 hours. AFAIK it's a 9 to 5 trip and they're not even offering the 3rd tank. I believe there is a 100-foot dive site there, but most of them are above 80 so dive times can run long... no idea if they limit them to an hour or what.
  4. KentB

    KentB Barracuda

    # of Dives: 200 - 499
    Location: Rather be under water
    Dollar value is not really relevant, It just comes down to how much money said person has.

    I'm a new diver and have a perdix AI that replaced a geo 2
    While I may not "deserve" or "need" the perdix it's much easier to read and navigate underwater. The AI is very nice as well. And so far it was worth the cost for those 3 things alone.
    Plus it also keeps prices down, if only " deserving " divers purchased expensive gear it would be wayyyyyy more expensive.
    I get where your coming from though I ride downhill mountain bikes and it kills me when I'm in the lift line at whistler and I see a 10 year old kid riding a $14000 mountain bike.
    RainPilot likes this.
  5. Neilwood

    Neilwood Loggerhead Turtle

    # of Dives: 50 - 99
    Location: Scotland
    It also depends a lot on the viewpoint of the person purchasing. I will pay what I need to to get the piece of kit that does the job best for me. I know where you are coming from re the kid with the $14K bike though - daddy's money must be great.

    My take as a firmly recreational diver with absolutely no plans to go tech at all and a prospective Perdix owner (I have pretty much decided it is what I want but need to get around to buying it):
    1) I dive in UK waters which means that visibility can be anything from 1 foot to 60 feet or better. If it is low, you want a computer that is easy to read.
    2) I dived with a mate who had an EON steel last year - I could read his computer better at 15 feet away on a typical UK sea dive than I could read mine (Cressi) at about 2 feet.
    3) The feature set of compass and AI add value as far as I am concerned - less gear to have to wear and slightly less task load (all the info is in one place).
    4) The LED screen is viewable in all light conditions - compared to the Cressi where I need the backlight (which is button operated) in a lot of situations (and sometimes where I don't want to have both hands operating the computer such as ascent/descent, holding a line on a stop in choppy waters etc).
    stuartv likes this.
  6. Aqua-Andy

    Aqua-Andy Solo Diver

    # of Dives: 500 - 999
    Location: Southern NH.
    I guess the way I see it is it is like someone purchasing a $3000 gaming laptop and only using it to surf the net. I don't look at my computer that often, If I have no deco time, total time, depth and temp I happy. Just don't have use for more than that on a rec dive.

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