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Water temp considerations

Discussion in 'General Scuba Diving' started by Alan Davies, May 16, 2017.

  1. Alan Davies

    Alan Davies Member

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    Hello I'm looking to go to vobster quay this weekend with a few friends and said I'd like to go to or around the 18m which I'm allowed with my ow but one of my friends that is much more qualified than me said I would not b going that deep because of the water temp
    Can anyone explain this
    I'm not questioning him at all but would like to know for future diving
    Thanks
     
  2. Griffalo

    Griffalo Active Member

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    The water is colder the deeper you go. I wouldn't normally notice the difference at 18m but I don't know Vobster, don't know you or what you'll be wearing. all of which could make a difference.
     
  3. jb2cool

    jb2cool Moderator
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    It's called a thermocline, warm water on top, cold water beneath. As you go through the year and the water warms up the thermocline gets deeper.

    Other 'clines are.

    Halocline (fresh water floating on top of salt water)
    Chemocline (where there is a chemical layer (Typically hydrogen sulphide) between water layers)
     
  4. Tel

    Tel Super Moderator
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    Vobster has noticeable thermoclimes.

    Vobster is a spring fed quarry with little actual water movement so the water acts more like layers.
    The difference between can be quite dramatic in the summer you can be in a semi-dry, no hood or
    gloves at 20 degrees, but at 30m+ a drysuit and the works .The bottom never gets much above
    6 degrees even in summer.

    The site has a road that leads down to a terraced area with the plane etc. at just over 12m. This is a safe
    environment as it has a hard deck, so get it wrong and you won't be going any deeper..

    Over this it drops down to about 22m, so at 18m you won't get there anyway which makes it a wall dive.
    More towards the West of the site it's 26m drop and all wall anyway.

    Bottom line is that you'll be on the 12m ledge or at 12m on the wall, no advantage to goto max of your
    grade at this point and as it's a new site (to you) always better to play it safe.

    As a relatively new diver i'd advise going in the confined area (ask in the shop if this is ok) which drops
    down to 4m. It's great for doing a buoyancy check, ensuring kit is trimmed right and all is ok. Once
    sorted after 5 mins can break out of there and carry on down to the 12m ledge.
     
  5. Griffalo

    Griffalo Active Member

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    ..and incline - where you swim uphill
     
  6. Tel

    Tel Super Moderator
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    Yep this bit is important for a new diver same as the wall and doing a vertical ascent.
    If using the suit for squeeze and warmth go through the clime you add gas to the suit to compensate,
    but this is also round about the time that the diver might be adding some gas to take care of compression
    etc. The upshot is that when ascending need to be careful that his gas is allowed to vent, so build in a
    stepped approach going up say 3m, stop briefly check neutral then again. So upto 9m stop, upto
    6m stop, check computer, do safety etc. goto 3m stop. Some comps will ask this anyway, but it's always
    a good idea as this is the bit where any remaining gas will be expanding the most and that stops any
    acceleration + it makes you feel better, less stress on the body and even means you can get in the
    face to face position so you can look over your buddies shoulder working together you get a 360
    degree look at any potential hazards also known as boats :)

    This way you don't get surprised by that failed to dump gas expansion and besides it's a much more
    deliberate and measured way of doing an ascent :)
     
    Griffalo likes this.
  7. Alan Davies

    Alan Davies Member

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    Thanks guys
     

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