As The Kraken said you need what you need to be neutral at you 15 foot stop. I'd extend that to say you need enough weight to make an orderly ascent after the 15 foot stop. With an empty BC you should gently break the surface after a slow final ascent. You can then inflate your BC for surface floatation. This event is what you need to set your weights for. At 15 feet you will be slightly negative and be able to make a safe controlled stop. Where you put the weights for the sake of trim is another discussion. This is most commonly accomplished with an end of dive weight check, bobbing plumb, relaxed, averaghe breath, no kicking at eye level to the surface with 500 PSI in the tank. As you breathe you mask lenses will go full under and full out of the water, more or less.
Now, what about the start of the dive. The good news is that you have almost 6 extra pounds of air squeezed into that cylinder to make you heavier at the start of the dive. The bad news is what I call stowaway buoyancy. Small amounts of buoyant air is trappped everywhere. My wife's Seaquest DIVA-LX is notorious for this, I can see it just dunking it in my rinse barrel, it sits there lika an alka-seltzer. I have heard this is common to some other Seaquest models, I don't know about yours. No to worry, you can deal with this. The same is true for your suit, the fabric and little pockets of air that will get displaced in the first moments of the dive. Then there is the entrapped gas in the neoprene that gives it the insulating value, this you need to live with.
As The Kraken mentioned the other challenge is your breathing, you're new and you're excited about entering the underwater realm. This is normal but it can easilly add 2-4 pounds of buoyancy to you at the critical moment.
So what are you do, get out there and make your next dive, do a thorough buoyancy check at the end of the dive, get the weight down so with 500 PSI you can barely be in control all the way to the surface to the end of the dive. This is the bobbing at eye level........ deal
Next dive, Get in the water, from a boat or shore, snorkel around for a good 5 minutes. This will let water saturate some of your gear and it will start to relax your breathing.
Once you are wet and mellow do your final buddy check, take your regulator and breathe face down for a minute or enough to get comfy. Give a final descent signal, dump all of your BCD air, remember you may need to twist to achieve a propper high point for air to exit. You should at least start to slump into the water, take a few nourishing deep breathes then exhale deeply, then keep exhaling. you should start down. When you need to breathe, make it a quick shallow breath, in and out, since buoyancy takes time to react due to inertia this need not halt your descent.
If that dosen't work do a valsalva to pressurize your ears a bit and kick your feet up in the air and do a little duck dive. Your legs will be out of the water in the air and are now true weight. Down you will go. Don't get carried away kicking down, switch to your prefered posture and complete the descent. Pay attenetion to your ears, equalize often.
Soon you will be adding air to your BCD to control your descent as you equalize your ears and watch your depth or level above the bottom on a shore entry. You will probably need to keep adding small amonunts of air even without a depth change for the first 5 minutes or so. this is because the stowaway buoyancy is escaping. Once you are past that you should be able to have a fine dive and can probably manage roaming in a 15 foot range just on lung volume varriance. Remember this is done with your diaphram, never by closing your throat.
For what it's worth and this all varries with exact gear and body type I'm 5-9, 200 LB. I wear 26 pounds of weight, soon to try 24 in salt water. I am diving an E7-80 which lets me wear about 7 pounds less weight due to favorable buoyancy propeties. My Full suit and hooded step-in have comparable neoprene volume. If I dove an AL-80 today I'd need to wear 26+7 =33 pounds to get the right effect, maybe 31 LB. So while YMMV there's a good chance that you can drop 10 pounds or so over time but some of that extra weight will keep you safe during your first exciting dives so go slow. As your suit ages it will also loose some buoyancy so dive often and check your end of dive buoyancy from time to time.
Take your time, pay attention to what's happening and have great, safe dives.
Pete
Tengai:
I am a newly certified OW diver. I need 42 lbs of weight to descend in 58ish degree saltwater!!! My instructor told me I should be using 10lbs less. She mentioned that the wetsuit needs time to fully saturate and that bubbles in the hood could be factors.
Also, she did say with time and practice I would be able to reduce the weight.
Help...What can and should I do to reduce weight? Do I need to reduce weight?
Here is my gear
BC-Seaquest Pro QD
Tank-al80
Wetsuit-7mm Henderson farmer john two-piece
Deep see hood, gloves and boots
U.S Divers blade fins
I am 5' 8" 210lbs
Thanks in advance