Night Dive Bouyancy

[Pook-60]

Howdy

I haven't got very many night dives under my belt but I've noticed when reviewing my computer dive profiles that my buoyancy at night can be pretty awful (especially at the start of the dive). My variation on my last night dive was ~35ft up and down with ascents/descents <10 ft per minute. It'll help to say that during the day my buoyancy is rock-solid and all my night diving has been shore-diving.

What I discovered is how dependant I am during the day on visual queues to tip me off that I'm ascending/descending. Given the reduction of those cues when relying on a narrow beamed light my weak areas are starting to assert.

During the dive I would do two things...refer to my depth gauge (but not constantly stare...I am there to dive after all ) and "listen" to my ears (a sure sign of depth changes but not what you would call accurate).

I know hugging the bottom will alleviate this issue but I don't think my dive buddy(s) would appreciate the silting. I reasonably assume the standard more dives = better diver but I'm curious if any "Boarders" can help me understand this a little better.

TX
Dane

 

[D_B]

not that I have much experience, but I would think that just having the bottom visible would help .. getting your buoyancy in control and solid before you swim off ... notice the little particulate matter in your light beam, it should be pretty stationary when light is pointed ahead, particles slanting up and your descending, slanting down and your ascending

 

[Gary D.]

You should practice the "XALER" method. If you can control yourself in the light the only difference is your nerves.

Gary D.

 

[redrover]

Hmmmm. General night diving for me is nothing diffrent. I did run into crappy buoyancy maintenance on the Black Water Dive and it annoyed the heck out of me. The Black Water Dive is 3 miles out over some 1,000’s of feet in the dark with the objective of viewing the pelagic little critters drifting and swimming around willy nilly. I assume not having a stable reference (the bottom or creature) was largely responsible. We are on a tether of sorts, a weighted line with a traveling biner line clipped on to diver and I was fine with the weighted line in peripheral vision.

My guess, for my experience, was the excitement had control of my breathing. Between the situation and critter thrill, I was reminded of how significantly the drawn out ohhhhs and ahhhhs of a pod of Spinners rising up encircling me wreak havoc on my no visual clue stops and I have to resort to frequent computer checks.

From the problem generally initially into the dive, night diving is new and exciting shall we say and you do have visual reference (bottom) perhaps you should up the attention to your breathing.
I use my ears too and find it requires more concentration as its much subtler input than visual.

 

[Doc]

I'm not sure of the environment, although you do mention "shore dives". Maintaining steady depth profiles along a coral wall or sloping field is fairly simple. Same deal as in day. Find a depth- then look ahead for the next landmark point that is at a level depth. Re-check your depth when you make that landmark- and so on.

In the unusual example give in the answer above, if you are intending to hover at 75fsw over a 2000 foot deep bottom, there are really only two ways to do it.

1) You can "tie off" to a secured "down line" physically or visually. It doesn't matter if this line is anchored to the ocean floor or just a weighted line hanging down from your dive boat or buoy.

2) Fly the plane on instruments. That is- you have only one job. Your compass and depth gauge. Assign one buddy this task- the other can look for Mr. Grey. Even if you see your desired large critter, remember... fly the plane.

As far as "visual cues" that you mention... Bravo! There are specific sedentary animals (corals) and flora that only live and thrive at very specific levels. As you learn these, depth by visual clues will become easier. Also be aware of light quantity and quality during the daylight dives- great indicators of depth.

Your audio method is not terribly reliable, difficult to master, but more power to you if you have a handle on this additional, useful tool.

 

[Pook-60]

You should practice the "XALER" method. If you can control yourself in the light the only difference is your nerves.

Gary D.

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not that I have much experience, but I would think that just having the bottom visible would help .. getting your buoyancy in control and solid before you swim off ... notice the little particulate matter in your light beam, it should be pretty stationary when light is pointed ahead, particles slanting up and your descending, slanting down and your ascending

Agree with you on the particulate matter D_B. That's something I can definitely watch closer and adjust accordingly. I noticed though that the visual on just the bottom with the limited field of view offerred by the light processes through my cranium as more 2-dimensional... I'll use the particulate approach on the next go! :14:

I'm not sure of the environment, although you do mention "shore dives". Maintaining steady depth profiles along a coral wall or sloping field is fairly simple. Same deal as in day. Find a depth- then look ahead for the next landmark point that is at a level depth. Re-check your depth when you make that landmark- and so on.....

...As far as "visual cues" that you mention... Bravo! There are specific sedentary animals (corals) and flora that only live and thrive at very specific levels. As you learn these, depth by visual clues will become easier. Also be aware of light quantity and quality during the daylight dives- great indicators of depth.

Your audio method is not terribly reliable, difficult to master, but more power to you if you have a handle on this additional, useful tool.

Thanks "Roatan"...I don't have a wall to refer off of but the flora/fawna reference tweaks a neuron I haven't used in a while. In fact...I think I'm missing great things to peek at during the day that deserve more attention.

Agree with you on "Ear Instrumentation Accuracy"

Appreciate the help guys...
Dane

 

[BuoyantC]

D_B is right on with watching the particulate matter. When I was a new diver in the Midwest and did my diving in lakes and quarries, viz was always low. Cuing off the bottom, I had thought my buoyancy was pretty good until I hit "clear" water. Geez, I was all over the place if I wasn't close to a reference.

My dive buddy had me do mid water hovers watching just particles. And as in most new environments, you learn to adapt. Eventually it becomes so automatic you don't even realize you are paying any attention to particulate matter.

Dennis

 

[TSandM]

Night dives are difficult, because we rapidly learn to assess the gradation in light as an orientation cue underwater, and at night, that's often not possible.

The best orientation cue at night is the bottom or other structure, but even that can confound you on occasion, if you are not sure what the orientation of the structure IS -- Is that rock sticking up from the bottom, or out from the slope? (Either of which is possible, where I dive.)

But a few things remain reliably constant, although they can be skewed a bit in heavy current. Bubbles generally go UP. Further, if you have a second stage with exhaust on both sides, bubbles should go up equally on both sides of your face. That gives you a reference for horizontal. Particulates in the water can tell you if you are moving with respect to them; they are generally pretty static. But they may not tell you if you are moving forward or back, or up or down. There, your ears and your drysuit (if you dive one) and the pressure of your gear on your back have to be your information.

Honestly, on ascent in midwater in the dark, I like to have a bag shot. The upline to the bag gives you a solid reference for what vertical is; the line on the bag gives you a solid reference for your depth.

I have seen two of the strongest divers I know (DoubleDip and KMD, people I can only aspire to emulate in the water) get disoriented with respect to depth in midwater at night. It's not easy.

 

[CODMAN]

If I may add my 0.02$, even though I'm not the most experienced diver (or night divere) here. I've really found the permanent backlight on my wrist computer handy for night diving. It stays lit all through the dive and I can take a quick look at it at any time, without having to activate a button. If I don't have any reliable visual reference handy, I can always check my buoyancy on the digital depth display on my wrist. It tells me quick enough just how neutral I am.

Cheers!

 

[spt29970]

Most night dives are conducted in relatively shallow water so that you have a square profile. Descend, hover over the bottom, and then ascend. During the first and last phases, you usually monitor your depth much more frequently than when you are hovering over the bottom.

As RoatanMan suggested, night diving in deep water is a whole different ball game. You really should be tied off. The "fly the plane on instruments" approach makes me nervous. The likelihood of getting separated from the boat goes way up. What if there is a current?

I should point out that the lack of visual references can also occur during the day. In general, I have very good buoyancy control, but on a trip to Roca Partida last year (in the Revillagigedos), the water was so clear, and the wall was so shear, it was hard to have visual references. On the first dive, I leveled out at 70ft, and fiddled with my camera for a couple minutes. When I looked at my computer, I found I was at 110ft, without noticing it! After that I kept a closer eye on the SPG and didn't have any more problems, but it highlighted the same fact that the original poster noticed. We are much more reliant on visual clues than we think.

Lastly, I should point out that using a drysuit can also help since depth changes rapidly translate to squeeze or expansion. This gives tactile feedback in addition to visual feedback.