Wetsuit buoyancy

[pelagic_one]

Hi all. My OW certification and all subsequent dives have been in warmer waters and the occassional thermoclines. I mostly use a rashguard. Now I have a Henderson 5mm full wetsuit to dive colder waters. To get a wetsuit that anywhere fits my frame from head to toe required a XXXL. The waist to legs area is a bit baggy, not as bad as riding britches, but not skin-tight and the arms are slightly loose. In a rash guard, I can frolick like a sea monkey in deep water. With the 5mm wetsuit I could not maintain depth or neutral buoyancy at all. Ascending from 20 feet to 19 feet would send me to the surface and descending one foot would sink me to the bottom. The power inflator and dump valve were required every moment in the dive. I had to watch my depth gauge continuously and make corrections with the BCD. Shallow and deep breathing were ineffective. Are my skills that bad or is the wetsuit loose fit the culprit?

How can divers in drysuits maintain any kind of neutral buoyancy going up and down with air in the suit?

 

[Vitesse2l]

I suppose the obvious answer is correct weighting and practice?

I do recall the frustration of losing my dive ninja powers when I first changed from wetsuit to drysuit!

 

[Thunder Struck]

Could be over weighted. Get a cylinder down to 500-700 psi and at 15’ dump the air from your bcd. If you start to drop like a rock too much weight. If you are corking it’d be too little, but you mentioned sinking quite quickly after descending a foot so I’m wagering on over weighted. You are compensating with the BCD but as you make that final part of the ascent the pressure differential is greater causing a greater expansion of gas in the BCD. When you dump air to compensate you wind up negative and ride the seesaw back down.

If you have a loose/baggy fitting wetsuit it’s easy to start overweighted because of the air pockets that will take time to flood during the dive. When they finally do you are over weighted for the dive. So if you don’t give them some time to flood before you descend you will think you aren’t weighted enough and go to add weight.

The 15’ buoyancy check is easiest when done with a buddy who you can hand weight off to and a float line that you can grab if needed. Dont load all your weights into the two BCD weight pouches. Scatter half in regular pockets or trim pouches that you or your buddy can pull them from.

Another technique to find your weighting is with whatever exposure suit you will be in, in waist deep water and with a buddy, take your weight pouches and hold them to your chest and exhale. If you sink fast take some weight away until you find out what it takes to get you to where when you give a good exhale you just start to easily go under. Have a buddy to help with adding or subtracting weights and help spot and bring you back up if you have too much weight. Then add or subtract additional weight based on cylinder buoyancy characteristics, if your BCD is positively or negatively buoyant.

From there keep a journal in your phone’s notes app where you can record what weight what equipment. Then you can simply add/remove weight based on changes of exposure protection or gear.

 

[Thunder Struck]

Another approach is to have about a football’s volume of gas in you BCD during the initial decent. More than that and you are too heavy. Less than that and you may not be able to stay neutral when the tank has become more buoyant as it empties. Towards the end of that dive at the 15’ 500 psi mark that football sized volume of gas you started with should be about gone as the buoyancy from the low cylinder makes up for it.

 

[Thunder Struck]

Oh, and drysuit diving and neutral buoyancy is easy peasy when properly weighted. To me it’s easier to trim out since I can move the gas where a need it. Move a little to my feet to get them to float up and keep my knees at 90° maybe shift some to my upper back or forearms to bring my head up a bit. Temperature aside, I much prefer diving dry over wet. While yes, it generally will take more weight (depends on how thick your undergarments are) it may be minimal or it could be a lot. But once you get it dialed in it’s smooth and easy moving around in the water.

And the less weight you are hauling around the less air you’ll need to burn to do it.

 

[lowwall]

Hi all. My OW certification and all subsequent dives have been in warmer waters and the occassional thermoclines. I mostly use a rashguard. Now I have a Henderson 5mm full wetsuit to dive colder waters. To get a wetsuit that anywhere fits my frame from head to toe required a XXXL. The waist to legs area is a bit baggy, not as bad as riding britches, but not skin-tight and the arms are slightly loose. In a rash guard, I can frolick like a sea monkey in deep water. With the 5mm wetsuit I could not maintain depth or neutral buoyancy at all. Ascending from 20 feet to 19 feet would send me to the surface and descending one foot would sink me to the bottom. The power inflator and dump valve were required every moment in the dive. I had to watch my depth gauge continuously and make corrections with the BCD. Shallow and deep breathing were ineffective. Are my skills that bad or is the wetsuit loose fit the culprit?

Once you've been under for a bit and any air pockets have migrated out of your suit, the drawbacks of a baggy wetsuit compared to a properly fitting one are that it leaves you colder and creates more drag. But it will have only minimal differences in buoyancy. Unless this problem only occurs at the very beginning of the dive where you could have a bunch of air trapped inside your wetsuit, what you are describing are the classic symptoms of being seriously overweighted. In other words the big air bubble in your wing is a more likely culprit than all the tiny ones in your suit.

So get your weight sorted out with a proper weight check at the end of a dive.

I'll also suggest sorting out your wetsuit fit. The best option if nothing fits off the rack is to have a custom suit made for you. But if you don't want to go that route, you might be able to find at least an improvement by getting different size separate tops and bottoms. For example you can pair one of Henderson's 5mm front zip jackets with a pair of 3mm paddleboard pants.

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[grantmac]

Likely overweighted.

 

[WillieJustice]

Oh, and drysuit diving and neutral buoyancy is easy peasy when properly weighted. To me it’s easier to trim out since I can move the gas where a need it. Move a little to my feet to get them to float up and keep my knees at 90° maybe shift some to my upper back or forearms to bring my head up a bit. Temperature aside, I much prefer diving dry over wet. While yes, it generally will take more weight (depends on how thick your undergarments are) it may be minimal or it could be a lot. But once you get it dialed in it’s smooth and easy moving around in the water.

And the less weight you are hauling around the less air you’ll need to burn to do it.

All true. But dialing in drysuit buoyancy takes a lot more practice than dialing in buoyancy in a rash guard or well fitting wetsuit. At least that is my experience.

 

[Saboteur]

There is an excellent, very detailed optimal buoyancy calculator spreadsheet created by @rsingler on this website. You can enter your details and get an estimate of what your weight requirements should be. You’ll want to do an in-water weigh check to confirm or adjust it.

 

[tursiops]

I'll also suggest sorting out your wetsuit fit. The best option if nothing fits off the rack is to have a custom suit made for you. But if you don't want to go that route, you might be able to find at least an improvement by getting different size separate tops and bottoms. For example you can pair one of Henderson's 5mm front zip jackets with a pair of 3mm paddleboard pants.

A similar solution is a Farmer John bottom and a separate top, either jacket or step-in long-sleeve top. Yje Farmer John dive syou double thickness over the chest& back so is a bit warmer.