Background: prepping in the pool for my upcoming July 13 live aboard trip on Okeanos II/Costa Rica/Guanacaste. Haven't been diving (other than pool) in quite a while. Abandoned effort to get larger capacity tanks rented on-site, so will be diving with AL80's. (the boat only has (2) AL100's available for rental and both are already spoken for.) After much analysis I decided having the boat try to obtain another AL100 from a land-based op not worth the trouble.
see my other thread on my analysis if you like:
Dilemma: AL80 vs AL100 ? Costa Rica/Okeanos Aggressor II typical fill pressures you've experienced?
So now it's up to me to get better gas mileage with the AL80.
Reports indicate the boat does do decent fills @ approx 3200 psi.
I prefer bigger tanks, but have used AL80s over the years on a few trips (Roatan-Co Co View / Bonaire (2) / Cozumel / Juliet-Bahamas / Juan Jose-Sea of Cortez / a few tanks on Nautilus Explorer when, near trip's end I switched from HP steel 100's Faber to AL80's because the Faber buoyancy sucked from both me and my female dive buddy).
If memory serves, on a typical ocean reef AL80 type dive, I'd average about 45 minutes.
I'm male @ approx 175 lbs. (I probably lose 20 pts right there in the gas consumption contest.)
I own and have dived pretty much every type/capacity single tank out there. I keep a basic spreadsheet for each trip recording wetsuit type-thickness/BP/tank type and lead weighting I used so I have a historical record of what seemed to work under different conditions.
I consider myself a very advanced recreational diver (with 500+ dives in open ocean good/bad and ugly conditions). However I'm going into this trip a bit rusty as haven't been on a trip in several years now.
Generally been a bit spoiled with access to larger tanks.
Did a 3 hr pool session yesterday to check out gear/refresh myself and also practiced the deep breathing techniques I've read about.
I was quite amazed at how I could easily only need breathe 2 times per minute! I developed a cycle of inhaling for 10 seconds (doing 4-5 inhale air sips) then exhaling fully for 15-20 seconds. I discovered each breath cycle lasted 25-30 seconds, which drastically reduced my air consumption!
That being said, doing those FULL exhalations messed with my buoyancy such that I found myself 'crashing' to the bottom (in slow motion). If I were kneeling on a sandy/rocky reef bottom, my new technique will likely work like a charm, but if I'm in the water column, the buoyancy changes may make my new techniques fail, unless I modify things by speeding up the exhale part of the cycle so there's less time to initiate the crash to the bottom sensation ?
I know that with increasing depth, the % pressure change per foot decreases, so I'm thinking the deeper I am, the less of a 'pendulum effect' I'd experience, it's just more pronounced up shallow, like the 12 ft. deep pool I practiced in yesterday.
I'm not trying to set bottom time records, just comfortably keep up with the other divers and get better 'mileage'.
Any thoughts or observations ?
Thanks in advance!