Uncontrolled descent

[vinegarbiscuit]

Five years ago, I was diving the U-352 off the NC coast. A large group was in line to drop off the boat, and my dive buddy was toward the end of the conga line while I was at the front. We did a pre-dive safety check at a distance with hand signals - very sloppy. He and I agreed that I would splash ahead and descend to the sub (bottom at 115') and wait for him rather than at the surface - it was a great day, good vis, no current - as we felt we were reasonably experienced divers and a decent buddy pair. I splashed and descended, and moved off to the side to wait for him to come down the descent line. A few minutes later I saw this ball of human limbs and dive gear dropping rapidly to the bottom, where it impacted in a huge cloud of silt. It turned out to be my buddy, who spent some time fiddling with his gear amidst the silt, before joining me. He said afterward that he realized as soon as he was in the water, and starting to descend, that he had forgot to connect his inflator hose, so he just let the descent go and enjoyed the ride. We still laugh about it.

I love the image of flailing limbs whizzing past you and the 'pouf' of silt as he hit the floor. "One day, we'll remember this, laugh, and nervously change the subject!" Or ball-bust from here to eternity, more like it...

 

[fnfalman]

My problem is not descending too fast, it is being barely able [and sometimes unable] to descend. If I am weighted in the average breath and empty BCD so I float with the water line at mid eyeball, I have a terrible time descending. I now have just over 20 dives. This is with an 8/7 mm hooded suit [we are diving in quarries in the midwest].

I find, if I check at the end of my best dives, during this weighting experimenting process, at the end of the dive, with the BCD empty and an average breath, my head is a foot or so beneath the surface. If I am weighted as you are supposed to be, at the end of a dive, as we approach the shore in reducing depth, once I get to about 8-10 feet I can't stay down. Too buoyant.

Once I get down far enough to compress the suit, then I descend fine. If I am not adding air to my BCD I will hit the bottom. The balance I want to achieve with respect to initial weight seems elusive.

I can start down, turn over and fin down, but that aggravates the ear equalizing thing, as it must happen quicker.

This is an interesting thread....

You're slightly underweighted. Throw in a couple extra pounds so that in the beginning with empty lungs and empty BC, you should float with your head barely underwater. Then just turn over and kick down until around 10-15ft which is where your wetsuit is compressed enough that you begin to sink slowly. Equalizing shouldn't be a problem if you equalize BEFORE turning over and duck diver down. When you kick down enough to start to sink, trim out horizontally instead of keep going down head first. You should have no problem with equalizing then.

You didn't mention that your tank is aluminum or steel. Aluminum tanks become positively buoyant at end of dive so you will definitely need a few extra pounds to compensate for the positive buoyancy.

You just need a few more dives under your belt, that's all. But it's good that you're not overweighted. That's the first step toward enlightenment. The next step is to learn how to establish neutral buoyancy at any depth and minimize air wastage by messing around with your BC's inflator/deflator.

If you don't like to duck dive, then just cup your hands and do the jumping jack motion to drive yourself down deep enough until the wetsuit compresses.

 

[Jeff Toorish]

Thalassamania got it exacty right.

Ironically, we were just talking about this the other day on a boat after a dive to a wreck, about 150' down. I doubles, we were adding air to drysuits and still sinking fast.

You can "dirt dart" to the botton if you don't add air to your bcd/drysuit early enough.

Jeff

 

[gndpdr]

it could be a new padi cert/patch "dirt dart"

 

[pittyyofool]

Buoyancy CONTROL is important, a Southern California example- One of the most popular oil rigs off out coast sits in 700 some feet of water.

I love Eureka, agreed not a place to dirt dart... although if you watch your gauge you can swim down to 120' fairly quickly and then work your way up scraping scallops. ummmm...

Sometimes it's fun to dive-bomb the bottom.

Very TRUE. there is a place for everything. I think dive-bombing the bottom is totally fine, along as you know your destination will be the bottom. If you plan the dive bomb and are braced for impact with the bottom. Whats the issue?

kick, breath, equalize, kick, breath, equalize, kick, check gauge :repeat :shocked2:

 

[MXGratefulDiver]

My problem is not descending too fast, it is being barely able [and sometimes unable] to descend. If I am weighted in the average breath and empty BCD so I float with the water line at mid eyeball, I have a terrible time descending. I now have just over 20 dives. This is with an 8/7 mm hooded suit [we are diving in quarries in the midwest].

I find, if I check at the end of my best dives, during this weighting experimenting process, at the end of the dive, with the BCD empty and an average breath, my head is a foot or so beneath the surface. If I am weighted as you are supposed to be, at the end of a dive, as we approach the shore in reducing depth, once I get to about 8-10 feet I can't stay down. Too buoyant.

Once I get down far enough to compress the suit, then I descend fine. If I am not adding air to my BCD I will hit the bottom. The balance I want to achieve with respect to initial weight seems elusive.

I can start down, turn over and fin down, but that aggravates the ear equalizing thing, as it must happen quicker.

This is an interesting thread....

That description is REAL common with new divers ... and most times the problem has nothing at all to do with weighting ... it's the result of your brain telling you that you ain't supposed to be here.

Two things to think about ...

First ... what are your feet doing? A lot of new divers tend to kick without realizing it. This has the effect of sending you up while you're trying to go down. Pay attention to your feet. In fact, try crossing your ankles at the beginning of the descent. It won't stop your "happy feet" ... but it WILL make you aware if they start kicking. If that occurs, make a conscious effort to not kick.

Second ... what are your lungs doing? Most new divers haven't yet learned that their lungs are another little BCD that they have to let all the air out of on the descent. Thinking about this is important ... because there's a correct way to breathe at the beginning of the descent that will make it a lot easier. When you're ready to descend, look at your buddy, give the "down" signal, raise your inflator hose, and as you press that deflate button take a big breath in and hold it ... just like you'd do on a weight check. Don't start to breathe out until almost all the air is out of your BCD and you're reaching just about eye level to the water. Then start a long, slow exhale. Keep breathing out until it feels like your lungs are empty. Then breathe out some more ... most new divers tend to retain some air in their lungs, because that's what we are used to doing on land. By doing it this way you are giving your body a chance to sink down a few feet ... where compression is your friend ... before you have to breathe back in. If you breathe in too soon it's like putting air back into your BCD, and you may find yourself going back up when you don't want to.

Once you've gotten a few feet below the surface, try getting horizontal, facing your buddy. This has several advantages ... it allows you and your buddy to watch each other as you descend ... it puts your body in the best position to control your descent rate (i.e. the "skydiver" position) ... and it lets you see the bottom coming before you accidentally kick it up with your fins. Breathe normally all the way down ... but when you're a few feet off the bottom take a big, deep breath in to help you stop before you reach the bottom. Then, as you need to breathe out, maintain your position with a couple short bursts of air into your BCD.

One of the primary reasons most new divers wear too much weight is because they have trouble descending. But more often than not, weight isn't their issue at all. They simply never learned the proper way to get down ...

... Bob (Grateful Diver)

 

[Diver0001]

I got into a conversation recently with someone about descending, and rate of descent. The remark was made that as soon as you are down a ways you should begin putting air into the BCD to control the rate of descent. It was also suggested that you could develop such a rate of descent that you might go too deep.

That's not the biggest reason you want to control your descent. You want to control your descent so you can HALT your descent if something happens like you can't clear your ears.

I admit to a lack of experience, but as I think about it, assuming you are properly weighted [not too heavy] and with a full tank, it would not be possible to develop an out of control descent rate from which you could not recover. I would think the friction between you and the water would serve to slow the descent rate, and you would finally stop descending.

Thoughts on this?

I've heard of this. Basically the idea behind it is that you could theoretically reach a descent speed that continues to compress your BCD faster than your inflator can fill it. In theory it might be possible but in practice I doubt very much that you could achieve that within the boundaries of normal recreational diving. Maybe if you were *vastly* overweighted, but that wouldn't be "normal".

R..

 

[DaleC]

My problem is not descending too fast, it is being barely able [and sometimes unable] to descend. If I am weighted in the average breath and empty BCD so I float with the water line at mid eyeball, I have a terrible time descending. I now have just over 20 dives. This is with an 8/7 mm hooded suit [we are diving in quarries in the midwest].

I find, if I check at the end of my best dives, during this weighting experimenting process, at the end of the dive, with the BCD empty and an average breath, my head is a foot or so beneath the surface. If I am weighted as you are supposed to be, at the end of a dive, as we approach the shore in reducing depth, once I get to about 8-10 feet I can't stay down. Too buoyant.

Once I get down far enough to compress the suit, then I descend fine. If I am not adding air to my BCD I will hit the bottom. The balance I want to achieve with respect to initial weight seems elusive.

I can start down, turn over and fin down, but that aggravates the ear equalizing thing, as it must happen quicker.

This is an interesting thread....

Bigsnowdog

If you do a weight check as described in para 1 you will be underweighted. While neutral you are not accounting for the 4-5lb's of positive bouyancy you will develop by breathing down your air. Compressed air has weight (roughly 5lb's for a Al 80).

I do a weight check at the end of the dive. In 10-15ft. of water I empty my tank(s) to 500psi and also empty my BCD/Drysuit. Then I adjust weight till I am neutral and add a lb or two for luck. That way I will not have a problem staying down at the end of the dive and will only be about 5-7 lb's (air + 1-2lb's) negative at the beginning.

 

[UCFKnightDiver]

A thought; If you dont have enough weight to get down to 15 ft or so at the beginning of your dive, or are barely able to you probably wont have enough to hold your 15 ft stop at the end. Your tank gets less negative as it empties. Throw a couple more pounds of weight onto your belt or bcd, its not that big of a deal and you should still be able to easily swim that rig up.

I dive a pound or two overweighted as the extra weight can certainly come in handy for an underweighted buddy, an out of control ascent ect. Also I dont have time to adjust weight for every different tank I use, as well as for salt vs fresh. Its really a non issue to me as it still is easy to swim the rig up even being a pound or two overweight.

Being just a bit overweighted is far better than being underweighted in my opinion!

 

[SNorman]

I descended with a friend one time who just sank like a rock to the bottom. I watched her all the way to the bottom (around 25 feet) and when she hit it looked like Wile E Coyote hitting the ground after falling from a cliff - a big puff of silt came out from under her in a big halo that looked like a smoke ring. I was too surprised to laugh until after the dive... LOL.