Help!! How to do a fast surface descent in a dry suit
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Even with drysuit dives where I need to descend quickly, I do them all essentially the same. I weight myself to be negative by the weight of my gas at the start of the dive. I mention this because some people choose to weight themselves slightly differently. After donning the drysuit during pre-dive prep, I always scrunch down into a ball and vent through the exhaust valve. This ensures that the exhaust valve is working properly, which is something that can be missed if you burp exclusively through the neck seal.
Once in the water at the descent point, I exhaust the air from the BCD and exhale sharply. This immediately causes me to descend in a head-up/feet-down vertical position. As soon as my head gets below the surface of the water, I rotate into a horizontal position. Shortly thereafter, I find myself adding air to my drysuit to offset squeeze and slow down my descent. I prefer to maintain a horizontal position during all phases of the dive because it helps distribute the bubble inside the suit better. I find that I can descend very quickly (pretty much as fast as I can equalize my ears) in a horizontal position. Personally, I dislike head-first descents in a drysuit. YMMV.
(FYI, I'm a single tank OW recreational diver, and this method of managing the initial descent in a drysuit works very well for me. People with other gear configurations, e.g., diving doubles, might find that other techniques work better for them.)
When we have to do a very fast drop for a deep drift dive, on to a wreck ( Palm Beach) , very fast currents can require the dry suit to be "pre-exhausted". If the boat can let you jump in 5 minutes prior to getting to the site, without tank on, so that you can immerse the suit completely and have it push the air out, this can work wonders.
It would be nice if someone could make a little pump you could connect to the inflator port of the dry suit, and pump out the air with....would have to be slow, to allow the restricted suit areas to pass the air....Water pushing all around you will always work better though.
When we have to do a very fast drop for a deep drift dive, on to a wreck ( Palm Beach) , very fast currents can require the dry suit to be "pre-exhausted". If the boat can let you jump in 5 minutes prior to getting to the site, without tank on, so that you can immerse the suit completely and have it push the air out, this can work wonders.
It would be nice if someone could make a little pump you could connect to the inflator port of the dry suit, and pump out the air with....would have to be slow, to allow the restricted suit areas to pass the air....Water pushing all around you will always work better though.
Why not hook a turkey baster type bulb to the valve, collapse the bulb, attach it to the nipple, press the inflater to release the suit air, release, repeat as necessary. It might take a little time but and accordion style bulb could be had I'm sure.
Ok, I looked online and found something that an MIT student had done with some off the shelf materials.
I fully agree with those of you who advocate feet first descents. yahoo! We don't want to suck air out of a suit though, especially before a descent as that will decrease our ability to kick effectively, will promote suit squeeze, and decrease our ability to stay warm. Here's some tips to getting a reasonable amount of air out of a drysuit, as well as how to descend without being overweighted.
First get good undergarments - we have found the best out there is Fourth Element's Arctic for cold water - they are much thinner than most winter weight undergarments but are as warm or warmer than the thick one pieces. Thin and well fitting - so no air pockets that we often had with the thick one piece undergarments. Thin means significantly less weight needed to be neutral. They don't compress like other undergarments, so less buoyancy changes with depth changes. You can purchase a different size top and bottom. Better fit means less trapped air. Viking Trellerborg switched to these undergarments becuase they're so good.
Next, once the drysuit is on, stretch to release air pockets and to put the arm pits and crotch of the suit in their optimal places. raise arms wide over head then slowly bend down to touch toes. Next burp - use left hand to release neck seal, put right hand on shoulder dump, go down to right knee, and twist your torso to left knee, thereby placing the arm dump at highest point. tuck chin. Every pint of air is equal to a lb of buoyancy so a pint trapped under the arm pits is a pound of lead you have to add. Then you have to deal with the buoyancy changes every time you rise and fall.
Next, if you're not wearing a good pair of rubber fins such as Scubapro Jet Fins (our favorite), Aqualung Rocket Fins, or similar fins, then you may need ankle weights. If you're wearing other fins then your feet are most likely positively buoyant. A 1/2 lb positive buoyancy in your feet can cause you to need 1-2 lbs extra on your belt becaue of how it will affect the way your body moves. We recommend the McNett durflex model of anke weights because the weight is evenly distributed around the entire diameter of your ankle. No area with webbing and no weight.
One of the main problems we see in the last few years with divers trying to descend is the air trapped in many backmounted BCD's- the dump valve is placed to low and then the inflator hose is strapped down to the front of the BCD trapping air between the dump and the velcro strap. BCD's like the Zeagle 911 can easily trap as much as 2-3 pints of air no matter how hard a diver tries to keep the dump at the highest point. We have the buddy squeeze the wings as the diver deflates, and are always amazed how much air comes out. Again - 1 pint = 1 lb of lead.
When you prepare to descend get alllll the air out of the BCD, cross your arms over your chest like a mummy and tense your arm and leg muscles, gently exhale, and you will slowly start to descend. If you need to, you can do a backwards ankle kick to use your feet to pull you under(keep legs straight). Contracting muscles makes you more negative - you decrease size without changing weight.
Let me know how it goes - hopefully downwards, safe diving always,
Do some practice dives and learn the tricks to your suit. Some suggestions: check dump valve and make sure it is working correctly, Some under garments block good air release (DUI), air goes up, if the air is around your neck it is not going out your valve, keep bubble at the vent, push down for fast release, there are valves that dump air faster (SI-Tech),check leaky inflator valve, if you carry an SMB make sure all the air is out, BCD all air out (sometimes we think it is out but it still has a bit left in the wing, exhale and relax. Make sure you know that you are weighted properly. You could try the skin diving technique where you bend in half, head down to the sea floor, lift legs straight up, and this added weight of your legs up propels you down to the ocean floor and continue swimming down. Have fun!
I fully agree with those of you who advocate feet first descents. yahoo! We don't want to suck air out of a suit though, especially before a descent as that will decrease our ability to kick effectively, will promote suit squeeze, and decrease our ability to stay warm. Here's some tips to getting a reasonable amount of air out of a drysuit, as well as how to descend without being overweighted.
First get good undergarments - we have found the best out there is Fourth Element's Arctic for cold water - they are much thinner than most winter weight undergarments but are as warm or warmer than the thick one pieces. Thin and well fitting - so no air pockets that we often had with the thick one piece undergarments. Thin means significantly less weight needed to be neutral. They don't compress like other undergarments, so less buoyancy changes with depth changes. You can purchase a different size top and bottom. Better fit means less trapped air. Viking Trellerborg switched to these undergarments becuase they're so good.
Next, once the drysuit is on, stretch to release air pockets and to put the arm pits and crotch of the suit in their optimal places. raise arms wide over head then slowly bend down to touch toes. Next burp - use left hand to release neck seal, put right hand on shoulder dump, go down to right knee, and twist your torso to left knee, thereby placing the arm dump at highest point. tuck chin. Every pint of air is equal to a lb of buoyancy so a pint trapped under the arm pits is a pound of lead you have to add. Then you have to deal with the buoyancy changes every time you rise and fall.
Next, if you're not wearing a good pair of rubber fins such as Scubapro Jet Fins (our favorite), Aqualung Rocket Fins, or similar fins, then you may need ankle weights. If you're wearing other fins then your feet are most likely positively buoyant. A 1/2 lb positive buoyancy in your feet can cause you to need 1-2 lbs extra on your belt becaue of how it will affect the way your body moves. We recommend the McNett durflex model of anke weights because the weight is evenly distributed around the entire diameter of your ankle. No area with webbing and no weight.
One of the main problems we see in the last few years with divers trying to descend is the air trapped in many backmounted BCD's- the dump valve is placed to low and then the inflator hose is strapped down to the front of the BCD trapping air between the dump and the velcro strap. BCD's like the Zeagle 911 can easily trap as much as 2-3 pints of air no matter how hard a diver tries to keep the dump at the highest point. We have the buddy squeeze the wings as the diver deflates, and are always amazed how much air comes out. Again - 1 pint = 1 lb of lead.
When you prepare to descend get alllll the air out of the BCD, cross your arms over your chest like a mummy and tense your arm and leg muscles, gently exhale, and you will slowly start to descend. If you need to, you can do a backwards ankle kick to use your feet to pull you under(keep legs straight). Contracting muscles makes you more negative - you decrease size without changing weight.
Let me know how it goes - hopefully downwards, safe diving always,
You know, this idea is common in still water baby dive sites.....But, advocating a feet first descent means it would be impossible to be dropped from a dive boat on a fast drift current adventure dive, and expect to be anywhere near where the boat captain wanted you to be when you near the bottom.
The OP was specifically talking about this kind of dive.
Take a dive off of Jupiter, like the Hole in the Wall. Top of ledge wall is 112 feet deep..Bottom of ledge wall around 140 to 145....Drift East with current 200 feet and it could be 160 and fairly blah looking sand and patch reef ( though good for lobsters).
The boats doing this dive will generally drop a group that in 2 minutes or less they will be near bottom. There can be a surface current going one way, and mid water current running 45 degrees to East or West, and there is usually a north bottom current.
The BEST way to near bottom close to the Cave ( which is the objective on this dive) is to go down like a rocket.
A feet first descent means you will not be able to land anywhere near the divers that do this dive frequently, and easily. The chances of even seeing the cave would be poor.
There are MANY dives the feet first procedure would render "unlikely".
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Originally Posted by danvolker
