Free descent help!

[alex_can_dive]

Today I attempted my first free descent directly to 45ft and it was quite failure!

After the first 6ft or so, I was sinking like a rock - much faster than my buddies; too fast that I couldn’t equalize enough despite kicking to slow the drop. Naturally I added air to my BCD to slow my sink, which helped a bit then I started free ascent!

How do I do this? Are you supposed to add some air to BC while descending or not? If yea, how much? At what depth should start to add? I suppose one could work out the exact depths at which you should add a pump or two?

Previously, for boat dives, I used the anchor line to descent, or at some sites there were shallower area (usually 15ft) where we’d just drop to our knees and swim to deeper end. Never really had to worry about my descent speed before!

 

[Julius SCHMIDT]

Good on you for attempting something new. Remove one weight and try again. It will come to you. Judging how much air to inject to control your descent depending on the performance of the bc is also a learned skill

 

[lowwall]

This is life with a thick wetsuit. You lose a huge amount of buoyancy as you descend, especially in the first 30'. You've discovered that 6' is too far without adding a little air, so do it at 5'. It might be easier to give your BC a little shot each time you equalize instead of trying to keep an eye on the depth while doing everything else. You just need to figure out a procedure that works for you.

FWIW, with a 3mm or less, I can descend slowly enough to equalize without adding air. I then add a 2-3 second blast maybe 15' off the bottom and fine tune from there. With a drysuit, I'm adding regularly on the descent to relieve the squeeze so it kind of takes care of itself.

 

[Centrals]

My own way:
1. Half inflated the BC before jumping into the water. I know it is enough to support me on the surface.
2. Look at my buddy and give thumb down signal to each other with right hand.
3. My left hand is on the power inflator and slowly release the air for the initial descent. Visual contact with the buddy.
4. Have to add air from time to time to slow the speed of the descent. Eyes on dc and buddy.
5. Right hand is for equalizing.
6. After adjusting to neutral buoyancy at pre-determined depth and check everything. Then exchange OK signal with buddy and swim off together.
7. My left hand is free at last.
8. Wear one dc on each forearm.

 

[napDiver]

Remember that it takes time for you to descend with a thick wetsuit. Bubbles are slowly coming out. This may take 10 - 30 secs.

From the surface dump just enough air to barely start sinking. Use your lungs to actually descend at the start. Try to maintain them at 25% capacity or less. Then continually add air quickly if you start to descend at a faster rate.

 

[MaxTorque]

It's an overreaction thing.

You were sinking, so you added too much air, now your ascending!

The trick, ime, is to use your lungs as the "quick response" buoyancy control. Most people can expand and contract their lungs by at least 2 to 3 litres by breathing at the "top of" or "bottom of" their lung capacity, and that is 2 or 3 kg of lift, a significant amount.


So, breath out to descend, and as you start to sink, breath in, if you start to sink too fast, take a full breath in to check your descent immediately, and THEN add a little squirt of air to your bcd. Basically you exchange the air in your lungs for that in your bcd until you are back breathing again from the middle of your lung volume. Think of it as using your lungs and the bcd. Use the bcd for slow changes, your lungs for quick ones.


Also, make sure you are not kicking your fins as you deflate your bcd, or you may actually let out too much air, then if you stop kicking , you suddenly sink. Many people have recommended puting and holding your ankles together as you leave the surface vertically to prevent ghost kicks that are so easy to do un-conciously!

As you sink you can aim to translate into the horizontal position slowly, aiming to be flat by say 3 to 5m depth or so. Being flat means you have less drag forwards/backwards, but more drag up down (because you present a larger surface area to the water in the flat direction) and this helps to slow down vertical motions, giving you more time to adjust your buoyancy).

And of course, being flat means you can fin fowards, and then your body acts like the dive planes on a submarine, and you can go up down by simply tilting / bending your body in the direction you want to go. It's surprising, with a very slow forwards speed you can really zoom up and down thanks to this effect, and offset temporary buoyancy errors to a large degree.


Finally, keep an eye on the depth reading on your dive computer. Open water decents where you can't see the bottom are surprisingly difficult because there is little frame of reference, so practice a descent using your computer reading. Leave the surface and try and stop at say 5, 10 and 15, depth, just using the computer

 

[rick00001967]

this is often a problem for new divers. many learn in the pool to dump all their air from the bc and "sink" to the bottom. they do their skills on their knees and then add air to the bc until they can swim around.

i like to tell my students they shoud never be "sinking". they should always be in control. you should be able to stop your descent at any time. you may need to equalize, or adjust your gear, or simply get your bearings.

you should never "crash" into the bottom. you should be able to remain in control at all times and hover off the bottom, or the wreck, or whatever target you are diving on.

perhaps try decending with an anchor line again. but this time pay very close attention to how it feels as you desend. slide your right hand along the line (be careful of it is not a clean line) and keep the left hand on your inflator. you can use the line to stop if you need help. you can also use the line as a visual reference to judge your speed. as suggested above, you can also use your dive computer to see the depth changes.

when you begin the descent, let out just enough air to the point where you can exhale and swim down the first 5 feet or so. as you descend pay attention to your depth and speed. again, you should be able to stop at any time. try to gently float downwards, adding air a little at a time as you go. do not wait until you are out of control. as mentioned above, do not forget that your lungs are very important in buoyancy control. use them.

lastly, be sure you are weighted appropriately. you should be able to hover at 10 feet or so with little or no air in your bc with a near empty tank.

 

[divinh]

When you're ready to go down, perhaps start releasing air from your BCD, but not immediately dump all of it? Since you haven't had enough experience to fine tune your weight yet, you're probably overweight. Release enough air to get moving and observe how fast you're dropping. Things react slowly underwater, so don't immediately compensate with releasing more air. If you feel you're dropping too slowly after 5 seconds, release more with two quick taps. If you feel you're dropping too fast, two quick taps on the inflator and wait to let things settle out. Main point is to let things settle before you react with the release or inflator.

Usually, I drop down to my desired depth, then use the BCD, to add or release air, to go neutral. From there, it's breathing to adjust depth. Sometimes, I will adjust with the BCD again, if I no longer feel neutral, but with quick two presses on the release or inflator and see how things settle before doing more. Be patient.

 

[TMHeimer]

Yeah, it can be interesting with a thick wetsuit, tons of weight, etc. To be honest, I don't recall doing a free descent to a bottom at 45 feet. But I've done it a lot to 20 and 30 feet. I make a game of it-- try to descend gradually and inflate the BC just enough to not touch bottom and start your horizontal dive. If you mess up, who cares?

 

[Bob118]

try descending with your inflator above your head and your finger on the button, and with your right hand on your nose. just keep equalizing as you go down before the pressure starts.