Did my first deco dive

[Deefstes]

I'm just so chuffed that I had to write a little something about it. My wife and I did our CMAS 2 star (AOW) qualification this weekend at Sodwana Bay. We had only three days for diving.

The first day never saw any launches as the seas were too rough. The second day we did two dives in fairly strong current, very unpleasant surge, and resulting bad visibility - but hey, bad diving is better than no diving.

The third day saw us do our first deco dive. The surf was a fair bit calmer than the previous day and we were optimistic when we saw the water having a nice blue colour. As we dropped off the boat though, I nearly spat out my reg in astonishment at the best visibility I have ever dived in. We were diving a 30m reef and you could see the reef from the surface. It turns out the visibility was upwards of 40m. On top of that the current was much weaker and the surge was all but gone.

What a dive! I saw my first Spotted Eagle Ray and Mantis Shrimp but the diving was just superb.

 

[chrisgp007]

Well done , yeah atleast u managed to pull in a dive overthere . Geez i feel like wantin to hit the road right now and get to sodies for some divin action and take some photos while im down there tooo.

 

[DivingPrincessE]

:huh: I'm confused? Was it a true decompression dive? Did you mean for it to be a deco dive or did you accidentally go into deco?

 

[Deefstes]

:huh: I'm confused? Was it a true decompression dive? Did you mean for it to be a deco dive or did you accidentally go into deco?

I'm not sure what exactly a "true decompression dive" is and how it differs from a "fake decompression dive" or whatever the opposite of "true" would be. This was a decompression dive in the sense that we incurred a decompression obligation as a result of the depth and bottom time. We planned for this decompression obligation and calculated before hand what the air requirements would be, what the critical pressure would be at which to terminate the dive etc. etc.

It was, in other words, the first dive on which I had to plan a decompression stop into the dive and actually did a deco stop as opposed to the customary safety stops.

Does that answer your question?

 

[DivingPrincessE]

I'm not sure what exactly a "true decompression dive" is and how it differs from a "fake decompression dive" or whatever the opposite of "true" would be. This was a decompression dive in the sense that we incurred a decompression obligation as a result of the depth and bottom time. We planned for this decompression obligation and calculated before hand what the air requirements would be, what the critical pressure would be at which to terminate the dive etc. etc.

It was, in other words, the first dive on which I had to plan a decompression stop into the dive and actually did a deco stop as opposed to the customary safety stops.

Does that answer your question?

Yup, I was just curious if it was a planned deco dive, or if was an "oops computer is telling us we're in deco" dive.

 

[Blackwood]

It turns out the visibility was upwards of 40m.

Insane. I'm jealous! I think my viz on Saturday opened up to about 12 feet or so after the first 15 feet of depth. Before that it was less than 7.

 

[ianr33]

I dont know much about CMAS but if you are planning on deco then it is not equivalent to AOW as taught by PADI etc as those courses are most definitely no deco.

And just to stir the pot a little: What gear were you using? Singles? Single with pony? Doubles?

Sounds like a fun dive

 

[Deefstes]

Insane. I'm jealous! I think my viz on Saturday opened up to about 12 feet or so after the first 15 feet of depth. Before that it was less than 7.

Did I mention the water temperature was 27 degrees? - and that's Celcius so we're talking 81 degrees Fahrenheit

Life is good!

 

[Deefstes]

I dont know much about CMAS but if you are planning on deco then it is not equivalent to AOW as taught by PADI etc as those courses are most definitely no deco.

And just to stir the pot a little: What gear were you using? Singles? Single with pony? Doubles?

Sounds like a fun dive

OK, I'm a noob so I'll bite

I don't know a great deal about the differences between various cert agencies. I do know though that part of the 2 star syllabus for CMAS is to plan and execute decompression dives to a depth no deeper than 30m.

The course material does not include training in the usage of doubles and their different configurations so any deco dive that you plan will have to be executable on a single cylinder. I have to say that I found this to be a bit strange because:
Using the Buhlman tables and assuming an average RMV of 25l/min, the shortest decompression dive at 30m (20minutes) would require a deco stop of 5 minutes at 3 meters and with an ascent rate of 10m/min and leaving a reserve of 50 Bar would require an 18l cylinder, not something that is very common around here. In fact, I don't think our dive charter has any.

Fortunately our RMV's are a fair bit better than 25l/min so we could pull this dive on a 15l cylinder but I just thought it strange that the course trains you how to calculate and plan deco dives which you will in most cases not be able to pull off.

So yes, the gear we were using were:
15l singles, no ponies, short hoses, BC's, no BPW's, no split fins, no force fins, no jet fins and as we surface I immediately donned my mask on my forehead

 

[TekDiveGirl]

I'm not sure what exactly a "true decompression dive" is and how it differs from a "fake decompression dive" or whatever the opposite of "true" would be. This was a decompression dive in the sense that we incurred a decompression obligation as a result of the depth and bottom time. We planned for this decompression obligation and calculated before hand what the air requirements would be, what the critical pressure would be at which to terminate the dive etc. etc.

It was, in other words, the first dive on which I had to plan a decompression stop into the dive and actually did a deco stop as opposed to the customary safety stops.

Does that answer your question?

Hrmmmm interesting --- this is qouted directly from the course standards found at :

http://www.cmasamericas.com/Assets/CMAS Standards/CMAS TWO STAR DIVER.pdf

Deep Dives.

No dives are to require actual stage decompression. However, simulated stage decompression may be added to the ascent of a no-decompression dive. Any simulated decompression time spent deeper than 20 feet must be included in the actual dive time. The instructor is to accompany students during the first training dive in excess of 60 feet (18 m) and on all dives in excess of 80 feet