zero visibility

[budgy]

The UK military divers have used inverted twins with a manifold to a single 1st stage. This isn't the standard manifold with a central isolating knob. Its basically two cylinders with din valves and a two into one manifold. The 1st stage is in the centre.
You have one cylinder open and one closed. No SPG necessary. If you start with 2X200 bar 10 litre cylinders You breath a cylinder empty, crack open the reserve cylinder and equalise the pressure and close the reserve, you have a 100bar in each. Breath it down empty, crack open the reserve and you have 50 bar in each cylinder and its time to go.

 

[k4man]

ok, silly question, maybe...

If you have TRULY ZERO Viz, and cannot see gauges, bubbles, other light sources...how do you know which way is UP???

 

[Diver Dennis]

If your buoyancy is good, then just take a full breath and you will start to rise or just put a little air in your BC.

 

[Gary D.]

ok, silly question, maybe...

If you have TRULY ZERO Viz, and cannot see gauges, bubbles, other light sources...how do you know which way is UP???

When your there you'll know. It would take a real moron not to figure that one out. You don't need to see your bubbles, just feel them. And moving just a few inches up or down will let you know.

Gary D.

 

[k4man]

When your there you'll know. It would take a real moron not to figure that one out. You don't need to see your bubbles, just feel them. And moving just a few inches up or down will let you know.

Gary D.

Although I may not know the answer, I have seen lots of morons in the water. THANKS!

 

[JungleJoe]

My comp woudl start screaming to go up (oceanic data pro plus II). I dive in 0 vis alot when I get to the bottom of the quarry nearby. If you are comfortable w/diving it's no big deal, more boring than not, but hey, it's bottom time !

I have also dove 0 vis for search and rescue, it's basically go by feel.

if you are a new diver or not 100% comfortable in diving, I do not recommend it, if you panic, you could get yourself into trouble.

in 0 vis, you can feel the bubbles and via that means I can control an ascent if needed, but I am rarely below 100 ft in 0 vis.

Also night diving gets close to it, and a ton of my dives have been night dives. you do have more vis tho, you can at least see where the light is shining.

wait till you get a 100+ or more dives under your belt and you are totally comfortable. you should
1) be able to know where any of your gear is w/o having to look for it, you should know all of your gear by feel

2) an audible alarm on a dive puter helps if you can't manage your air decent

3) you have to have enough experience and dive time and be totally comfortable in ANY situation before you hit a 0 vis

4) if you are diving with a buddy, rope up

I am sure there is more, but that's my 2 bar

 

[ReefGuy]

Whenever I dive, I check my gauges often. One of the things I do is tell myself how much air I'm going to have when I look. I've gotten to the point where I'm pretty accurate now.

As said before, in true 0 vis, holding your gauge or computer up to your mask will not work, at least not around here. There's so much crap suspended in the water that even the couple of millimeters between the gauge and the mask will render it unreadable.

When diving in this, I've got another diver right next to me, and we're tethered to a tender on shore with a safety diver ready to follow the rope down. We are in voice communication, and have a backup system by pulls on the rope.

What makes it really interesting is all of the stuff we come across. Due to the hurricanes (especially Charley in 04), there's lots of crap to work around, from roofs to all kinds of cloth and bags to lots of sharp, pointy unidentifiable things. Not to mention the stuff we are looking for.

Ascents never seem to be an issue, mostly we're doing arc searches where the end of the arc is the shoreline.

 

[John C. Ratliff]

I'm rather surprised that no one has mentioned using a J-reserve in zero visibility. Scubapro has one (or had one) which could be set for either 300 or 600 psi. Most are 300 psi for single tanks, or 500 psi for doubles. I have used them in the 1970s for search and recovery missions (dives) in zero visibility. They work well in that capacity; but either use them reversed (see this thread for a discussion on how to do this: http://vintagescuba.proboards2.com/index.cgi?board=instruction&action=display&thread=1160451692) or check them often to make sure that they have not been inadvertently tripped. There are still enough J-reserve valves around, and a few vintage (but very good performing) regulators with a J-reserve built in (the AMF Titian and the older Calypso-J are examples).

Concerning how to know which way is up, the bubbles will tell you if you are patient and feel for it.

Audio alarms on computerized SPGs don't work for me, as I dive cold water, and wear a hood for most dives. I cannot hear them with a hood on. But, the old Scubapro Mark VII first stage has a sonic alarm that can be heard with a hood over the ears. As a matter of fact, it can also be felt, and the breathing is sorta pulsing too.

SeaRat

 

[FredT]

A true Braille dive is one where there is "black water", defined as water that has no light penetration. If you submerge the top of your mask it's DARK. The small layer of water between the faceplate and instrument lens formed by the instrument bump guard with the instrument pressed against the faceplate will absorb all light. Even a large light is useless.This is the world many commercial divers live in. When doing recoveries in some really nasty water back in the dark ages I had a mask with a plywood faceplate. If it gets dark before you get into the water the games your mind plays on you go down, and the last thing I wanted was to have that water touch my eyes from a broken faceplate due to bumping into something (before the days of tempered glass faceplates).

Almost all Braille dives are done to complete a specific task. Gary's will normally involve finding a car wreck or body, in the oil patch it's pipeline installation or repair, rig inspection, or any other construction or repair job. You eventually get to where you can "see" what's around you by feeling the little currents on your skin hair if diving wet and warm. My last black water dive was to recover some seismic source "guns" that had slipped their tether and buried themselves about 10' deep into the firm mud in the bottom of a fresh water test pond. The guns and controllers were worth close to 100K. The dive was cold and wet, but since nobody had EVER been in this pond I chose to do it in t-shirt and shorts so I could "see" a bit of what was around me. Gear was a J-valved single tank, single hose reg with no pressure gauge or octo to minimise possible entanglements. The recovery took about an hour once the gear and tenders and hoisting equipment were set up.

They were refilling that pond from a deep artesian well putting out water at about 40°F. Surface water wasn't bad, but the termocline, and black water started about 2' down. I thought I'd have to sit down to pee for a week!

FT

 

[Dive-aholic]

I thought I'd have to sit down to pee for a week!

FT

Sorry, Fred, but that's just too funny!!!