How much negative buoyancy can you swim up with?

[Graveyarddiver]

As a lifeguard I was able to tread water with a 15 lb weight. I imagine with fins and wet suit I could make it to about 25 comfortably. Of my life depended on in I'm sure more would be feasible, or I would start ditching gear that's negative.

 

[dmaziuk]

Did not want to hijack a parallel thread but there seems to be a lot of difference in peoples perception of how much negative buoyancy can a diver swim up with in the event of a wing failure? Curious.

I do 2 10-lb bricks in the pool sometimes, just for practice. I can stay up with them for a little while, but I never tried to find out for how long exactly. Nor how much I can swim up with. This is in a 12-foot diving well in speedos, using only legs as my hands are busy holding the bricks.

 

[TMHeimer]

I don't know what I could do. I dive with a farmer john 7 mil wetsuit and 42 pounds of lead. I have had no problem starting my swim up from 20 or 30 feet. Of course, my BC is not completely empty while on the bottom, so I usually release some air at maybe 5 feet from the surface. Always mean to try it with completely empty BC but forget to. I will make a note to do this.

I tried it today and had no problem ascending from my (max) depth of 15'. I'll have to try it again in summer from deeper. Just to *&+^ing cold diving wet now after walking through snow to get to the beach. 'Tis the time of year for just one "in & out" 20 min. dive.

 

[Kevrumbo]

 

[Bierstadt]

I don't know what I could do. I dive with a farmer john 7 mil wetsuit and 42 pounds of lead. I have had no problem starting my swim up from 20 or 30 feet. Of course, my BC is not completely empty while on the bottom, so I usually release some air at maybe 5 feet from the surface. Always mean to try it with completely empty BC but forget to. I will make a note to do this.

Wow, that is a lot of lead! I'm sure your buoyancy is fine, but boy, how do you distribute all that weight? Harness, or bcd pouches and belt? How does that feel on the bottom buoyancy-wise? I have yet to dive more than a 7mm.

 

[TMHeimer]

Wow, that is a lot of lead! I'm sure your buoyancy is fine, but boy, how do you distribute all that weight? Harness, or bcd pouches and belt? How does that feel on the bottom buoyancy-wise? I have yet to dive more than a 7mm.

Yeah, I hear that a lot. Actually, it's fine on the bottom, as a collector I spend basically the whole dive there. Also good in the very shallow dives I do, but that may be due to a lot of experience at 15-30' depth dives.

I have 2 ten pounders in the BC pockets, 4 lbs. in each of the back (up high) trim pockets, and the other 14 lbs. in my pocket weight belt. Suspenders for the belt as I gave up tightening belts and busting a gut over a decade ago.

Just the other day I was checking the old Adventures in Diving PPV section "Basic Weight Guidelines" and come up with this:
10% of 190 lbs. body weight = 19 lbs.
7 mil wetsuit, hood, gloves, add 5 lbs.
salt water diving with 190 lbs. body weight, add 7 lbs.
AL tank, add 5 lbs.

This comes to 36 pounds.
I note that for the 7 mil wetsuit it could mean a one-piece and I use farmer john, so that may be different. May add several pounds, not sure which suit they mean.
When I was diving in my old farmer john I was at 37 lbs.
The new one is far more buoyant, thus I need 42--could not get down with 37 without fighting and clawing on rocks.

Anyway, There was a big thread on this a while back. I have found that at least two instructors on staff here use about the same weight when in a 7 mil farmer john. Of course, they almost always dive dry.
Actually, I haven't done a proper weight check since OW 13 years ago. I just added a pound or two each dive until I was back to where I was with the old wetsuit.
Now of course, you're supposed to add 5 lbs. if doing a proper weight check with a full tank. To be honest, I don't know how that works out for me. The rare time (maybe avg. once a year) I have done deep boat dives I haven't had any problem being too light while at the safety stop. That would suggest that I'm overweight when starting out. But that doesn't seem to be the case.
Experienced divers may ask if I exhale on initial descent--yes.

 

[CT-Rich]

Hmmmm..... perhaps this is why I have never been a huge fan of non-ditchable weight.

 

[cool_hardware52]

Hmmmm..... perhaps this is why I have never been a huge fan of non-ditchable weight.

Ditchable vs non ditchable is not IMO a simple yes or no question.

Consider the warm water diver wearing little or no exposure suit. They may well not need any ballast in addition to their reg and empty cylinder. Do they need ditchable weight?

Or the diver doing mandatory decompression dives. Losing ballast could well be a greater risk. Do they need ditchable ballast, or should they carefully consider some form of redundant buoyancy?

In general for cold water recreational single tank divers I like to see ballast roughly equal to the weight of their gas carried on their person in a manner that allows it to be released. Primarily to allow any rescuer to easily get the diver positive at the surface without having to know anything about their BC, or in the event of a failed BC.

I cringe every time the question of ditchable vs non comes up because the answer isn't yes or no, it's maybe and too many are looking for a single snappy answer devoid of understanding.

Tobin

 

[CT-Rich]

Ditchable vs non ditchable is not IMO a simple yes or no question.

Consider the warm water diver wearing little or no exposure suit. They may well not need any ballast in addition to their reg and empty cylinder. Do they need ditchable weight?

Or the diver doing mandatory decompression dives. Losing ballast could well be a greater risk. Do they need ditchable ballast, or should they carefully consider some form of redundant buoyancy?

In general for cold water recreational single tank divers I like to see ballast roughly equal to the weight of their gas carried on their person in a manner that allows it to be released. Primarily to allow any rescuer to easily get the diver positive at the surface without having to know anything about their BC, or in the event of a failed BC.

I cringe every time the question of ditchable vs non comes up because the answer isn't yes or no, it's maybe and too many are looking for a single snappy answer devoid of understanding.

Tobin

At the end of the day, the last option for a diver is to ditch weight at depth, embolism is a serious danger for dropping weight a depth. With the catastrophic BCD failure that may become an option of last resort. Risking barotrauma is better than drowning. Many divers can not afford $1000+ cost of a dry suit. Most are never going to wear twin steel 120s. Ditchable weights are a low priority for cave divers because that would be reaallllyy bad. Lots of special cases, absolutely, but this is a basic forum.

For the vast majority of situations a diver will face, ditching weight is about staying at the surface under adverse conditions while waiting for a pickup or swimming to shore. My BCD failure happened at night in 30’ of water 75 yards from shore. I could swim to the bottom, midwater or surface, getting up and down was never the issue. Staying on the surface where my buddy was a priority some of the weight I dropped with my belt and my buddy, who could fully inflate his BCD carried my pouches. A drysuit would have made it a non issue. This pretty typical situation for most divers, at the surface and you want to stay there with the least difficulty as possible.

When I said I am not a fan of unditchable weight, I was speaking for myself and my type of diving. The OP on this thread asked how much could be swum up. Once at the surface, the question becomes how long can you stay there. Unless it is a bar of silver from a Spanish galleon, keeping the weight you just had to swim up is moot. If you want to stay at the surface dumping something, whether it is a belt, pouches or BP/W is entirely up to the diver and how much he wants to go home that night. I have swum up an 8lb anchor without pumping up my BCD (I am not a lift bag). After I clipped it off I went back down and continued the dive.

 

[cool_hardware52]

At the end of the day, the last option for a diver is to ditch weight at depth,

What if the only ballast the diver is carrying is his reg and tank? Warm water resort diving is hardly an exotic niche practiced by an elite minority of divers. Should they ditch that at depth, or swim up a few lbs and continue to have a working gas supply? Again no universal answer.

embolism is a serious danger for dropping weight a depth. With the catastrophic BCD failure that may become an option of last resort. Risking barotrauma is better than drowning. Many divers can not afford $1000+ cost of a dry suit. Most are never going to wear twin steel 120s. Ditchable weights are a low priority for cave divers because that would be reaallllyy bad. Lots of special cases, absolutely, but this is a basic forum.

True, but statements like "I never liked weight I could not ditch" leaves the impression, particularly for new divers, that all ballast should / must be ditchable.

For the vast majority of situations a diver will face, ditching weight is about staying at the surface under adverse conditions while waiting for a pickup or swimming to shore.

Also True, exactly why I recommend single tank cold water divers have at a minimum ballast roughly equal to the weight of their gas on their person (belt or weight harness) configured so they can ditch it.

I speak with many new divers. Most a confused about ballast in general, and ditchable in particular.

"My instructor said I need at least XX lbs ditchable!!"

Where did you train?

"In a local quarry"

Where are you planning on using the BP&W you are interested in?

"In the tropics"

Er, ah ok, you probably won't need much ballast beyond a backplate and reg.

"But, but, but my instructor said we need at least XX pounds to drop so we can get to the surface, should I add a weight belt so I have something to ditch?"

Sigh.....

Tobin