I would first like to say excellent question.
Your concern is that you are diving at possibly 120 or 130 ft.
At 120ft for 32% you would have an O2 exposure of 1.5
At 130ft for 32% you would have an O2 exposure of 1.6
Max exposure at 1.6 is 45minutes (total single exposure.)
Practical experience for Flower Gardens is the following-
65ft is the tie in that is 1.0 PPo2 (for 70ft.)
I would say that for the average dive you are looking for a depth of 85 to a max of 100ft.
For Nitrox divers the suggested PPO2 range is 1.2 to 1.4 during the dive.
A PPo2 of 1.2 is 90ft and 1.4 is 111ft. So that is really your floor.
If you felt for some reason you needed to drop to 130ft on the first dive then your decompression is going to catch you before o2 issues.
If
you made a six minute exposure at 130ft (1.6) you would be exposing yourself to 15% of you total daily exposure thats it. I would suggest not hitting 130ft. No reason to keeping it to 110 to 120 MAX.
At 1.6 this is considered the limit and that is not recommended for heavy activity underwater.
If you were to look at single Nitrox exposures (1 dive)
At a PPo2 of 1.2 you have 200minutes, 1.4 is 150miutes, and 1.6 is 45 minutes.
What I found was my average depth was 85ft at the gardens.
So that is basically the 1.2 setting at 90ft.
At Stetson bank that changes to 100ft and that results in a PPo2 of 1.3.
Most people use a PPo2 limit of 1.4 for actual dive time verses decompression.
If I could make a suggestion- use a Nitrox computer! If you do not own one RENT IT. It is worth the money hands down. Plus god forbid something does happen everything is logged through that little jewel for them to download later.
Since Flower Gardens is consider deep dive check the dive computer planner for each dive, compare it to your tables, and know what your NDL limits are.
Since it is a deep dive a few points.
1. Have a turn around tank pressure. For my first few dives I use the 3rds rules.
1/3 out, 1/3 back, and 1/3 for emergencies and slowwwww surfacing.
2. My first stop is at 60ft for a 100ft dive for 1 minute. Another option is to stop at three quarters of your total depth. 60ft dive my first stop is at 45ft for a minute.
3. Take your time on your ascent 30ft per minute rise MAX. You did the time- you take your time coming up. I typically stop at three or 4 places (60ft, 40ft, 20ft, 15ft)- the deeper stops are for only a minute to help your body catch up.
4. Make sure you do your stops at 15ft for how long you feel is necessary.
5. If you fall into decompression- follow the computer and take your time. This is the reason you have it. Upon exiting tell a surface divemaster. Your safety is their primary concern. They may have you sit out the next dive for your safety. Decompression diving is a class all to its own.
6. Enjoy your time in shallow water- we saw some of the most interesting things while hanging on the line.
7. Buy Dan before the trip, we never wish accidents but being prepared is the best.
To close personally, you would totally benefit from diving Nitrox at the gardens plus the END benefit is substantial. Get the computer!
I have to give thanks to Debra for getting me diving at the Gardens and it has been one of my favorite trips since.
Any questions, please feel free to give me a yell.
