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Estimating Current

Discussion in 'Basic Scuba Discussions' started by Silty Sam, Nov 25, 2019.

  1. Silty Sam

    Silty Sam ScubaBoard Supporter ScubaBoard Supporter

    # of Dives: 500 - 999
    Location: Great State O'Maine
    149
    43
    28
    Anyone have suggestions for estimating or measuring current on a dive?
     
    The Chairman likes this.
  2. JackOfDiamonds

    JackOfDiamonds ScubaBoard Supporter ScubaBoard Supporter

    # of Dives: I'm a Fish!
    Location: Israel
    341
    214
    43
    Throw your buddy in the water and look where he ends up :popcorn:
     
    EdC, jonhall, Dizzi Lizzi and 5 others like this.
  3. Silty Sam

    Silty Sam ScubaBoard Supporter ScubaBoard Supporter

    # of Dives: 500 - 999
    Location: Great State O'Maine
    149
    43
    28
    That will never work: my buddy is bigger than me.
     
  4. JackOfDiamonds

    JackOfDiamonds ScubaBoard Supporter ScubaBoard Supporter

    # of Dives: I'm a Fish!
    Location: Israel
    341
    214
    43
    Its all about leverage , use his size against him.

    Or just surprise Sparta kick
     
    EdC and wetb4igetinthewater like this.
  5. TMHeimer

    TMHeimer Divemaster

    # of Dives: 500 - 999
    Location: Dartmouth,NS,Canada(Eastern Passage-Atlantic)
    12,136
    2,621
    113
    I have thrown a stick in the water, but of course that is only the current on the surface.
     
  6. Silty Sam

    Silty Sam ScubaBoard Supporter ScubaBoard Supporter

    # of Dives: 500 - 999
    Location: Great State O'Maine
    149
    43
    28
    Right. We can measure boat speed with the GPS, but that is surface current PLUS wind, depending on what is going where.
     
  7. tursiops

    tursiops Marine Scientist and Master Instructor ScubaBoard Supporter

    # of Dives: 2,500 - 4,999
    Location: U.S. East Coast
    8,054
    5,747
    113
    Just stop kicking and be motionless, see how far you drift in, say, 10 s. If you drift, say, 2m, that is 0.2 m/s, which is about 0.4 knots.
     
    couv and Silty Sam like this.
  8. KWS

    KWS ScubaBoard Supporter ScubaBoard Supporter

    # of Dives: 500 - 999
    Location: SE TEXAS
    4,395
    1,033
    113
    1KT IS 6000 FT PER HOUR OR 100 FT PER MINUTE. ROUGHLY 1.5 FOOT PER SECOND. PICK UP SOME SILT DROP IT ANS LOOK AT T TRAIL AND NOTE THE TIME. OR IF DRIFTING WATCH HOW FAST LANDSCAPE IS GOING BY AND GUESS THE DISTANCE IN FEET THEN PER SECOND DIVIDE IT BY 1.5 ADN YOU HAVE IT. THERE IS ALSO A MARINER 3 MINUTE RULE YOU CAN EMPLOY ALSO WHICH IS I BELIEVE SPEED TIMES 100 YARDS IS THE DISTANCE YOU GO IN 3 MINUTES. 1 KT = 100 YRDS = 300 FT MOVEMENT N 3 MINUTES OR SIMPLER 100 FT PER MINUTE

    sorry for the caps
     
    Silty Sam likes this.
  9. nolatom

    nolatom Captain

    # of Dives: 200 - 499
    Location: New Orleans
    1,154
    523
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    All good (and also funny) answers above.
    Here's an old thread about how fast the average diver goes while finning comfortably/uncomfortably/maxed-out:
    Average Speed for a Scuba Diver
    It seems we amble along "averaging" about half a knot, and "fin purposely" to make one knot. This is a gross generalization and fitness/streamlining vary a lot. As a weekend duffer, I would find a half- knot current to be a lot, and at one knot I'd wonder why they let us jump in unless it was a drift dive, as I would struggle to just stay even with the boat, absent any handholds or wreck-type shelter.

    "100 feet per minute is one knot" is the basic thing for a non-metric English major like me.. Then as Turisops and KWS point out, you can break that down into smaller pieces. Let's say most of us are 5-6 feet (or about 2 meters) "tall", as a rough measuring stick. 100 feet per minute is one knot, so in one second you'd make 1.66 feet, and in three seconds about 5 feet. So one of my lengths in only 3 seconds while passing a reference point, that's about one knot, aack why am I here. In 6 seconds, that's better, about half a knot. Ten seconds, that's about a quarter-knot, noticeable but okay. No, I'll never win a math prize but it's doofus simple for me.

    Or, when in any doubt, always head up-current from the anchor line to begin with. If you get tired doing that, then be grateful you're not downcurrent.
     
    Silty Sam, Johnoly and VE7DAC like this.
  10. tomfcrist

    tomfcrist NAUI Instructor

    # of Dives: I'm a Fish!
    Location: Virginia, USA
    2,882
    1,780
    113
    Underwater, I classify current in the following categories: none, slight, swimable and hell no.

    On the surface I use my GPS to calculate 1 minute drift as shown above...but I use a coconut as the marker. Drop the coconut and a GPS mark on the site. Drive boat to the coconut after a minute and see how far away you are from the drop point....100 ft per Kt of surface current.
     
    Dizzi Lizzi and nolatom like this.

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