Buoyancy problem I can't solve

[scubadiver888]

She's wearing a brand new 7mm suit with a used 3mm hooded vest.

I don't suppose the rental was a farmer john + jacket and her new suit was a jumpsuit?

He didn't say what the rental outfit was but the new gear was 10 mm on the core.

 

[aquaregia]

I guess what I mean is that (in my experience) a farmer john is a lot more neoprene than a jumpsuit, so even if the rental was beat up it might be more buoyant than a new jumpsuit (+vest).

 

[g1138]

Dive buddy is using a steel 80 or 85. I'm guessing it's -7 full.

Steel plate and weighted STA. So we're at -19 lbs.

First dive she used I think another 16 lbs of lead so -35 lbs.

She's got a 30 lb Halcyon rental wing.

She's wearing a brand new 7mm suit with a used 3mm hooded vest.

These are the facts and they indisputable. ;-)

She descended (~ 50 fsw) and was quickly separated from 2 of the four divers she was with. She did have a buddy with her, though. She was immediately uncomfortable and needed assistance with ascent. Once on the surface, the comments made suggested with a full BCD, even finning, she couldn't surface.

I was shocked because while 16 lbs was way too much, with the suit/rig she still should have been able to surface. I'm thinking it was more of a mild panic. Any suggestions or is it likely she simply couldn't swim it up? She's in good shape so that's not a factor. No....I wouldn't have let her go with that much had I known.

Hopefully to keep this simple I'll clearly state the question:

1) Given the amount of weight (lead/plate/STA), the wing and the amount of neoprene, should she have been able to swim to the surface?

2) If so, what might have been stopping her? I thought about down current but given the location, not likely.

One input I may offer is from personal experience.
At the time my wetsuit was only half a year old. It's a 7mm Farmer John so you're talking about 14mm of neoprene on the chest. I was also wearing a 3/5mm hood, 3mm gloves, and 5mm booties.
I was using a 28lb back inflate BC, Faber Steel 72 (it's actually 71.~, supposidly), and 16lbs of weight total (split 12lbs belt, 4lbs BC).
This is a salt water configuration.
On the surface I have to pike dive till my center of mass is about 5ft before I feel any loss of positive buoyancy.

That being said, one time, less than 5mins into my dive I lost my weight belt at 30'.
So now I have an empty BC, full St 72 tank, and 4 lbs of weight on me.
Turns out I was neutrally buoyant.

Back to your post:
At 50' I'm sure the women's 7mm suit would have been completely compressed, and any buoyancy it normally provided at the surface would have been lost.

I'm not sure if bubbles in the neoprene compress or actually leave the suit.
It probably changes as the suit gets older.

Edit:
I forgot to add.
Changing her suit could have affected her mentally. Some suits feel more constrictive than others and different style can change your mobility and even mentality.
I wasn't able to access my BC zipper pockets effectively until I changed into a 4/3 covered with a 7mm jacket.
It could have just been the combination of suit compression, unfamiliarity with the new suit plus newfound mobility (or lack of), plus a little more weight than necessary.

Has she ever used a hooded vest before?

 

[lowtech]

I'll toss a couple things out there...

Your biggest change in bouncy is in the first 33ft and with a new, more buoyant, wet-suit, perhaps that change in buoyancy made her feel as though she could not swim up.
Some mild panic, not finning properly, trying to work the inflater, maybe the wing wasn't "completely" full at depth etc...
Did you notice the wing burp at all on accent, or was it purged manually on the way up?
Also, what TSandM said, the heavier Faber steel tanks can be twice as negatively buoyant. Something like -13# full, from what I recall.

 

[on_two_wheels]

Again, what SHOULD have been done is an already known variable. I have the answers I need to moud a pretty sound evaluation. Thank you everyone.