Dive, Safety Stop, No Surface Interval,Dive, Safety Stop, Surface?

[Ephesmax]

I'm a new diver with less than 10 dives. I certified last october here in Fl and spent all winter reading books like: shadow diver,scuba confidential, dark descent and so on. I realize they are not a replacement for experience but i feel I have a basic understanding of the sport.

I dove with 4 divers I was paired up with another diver I knew but never dove with before. We were diving the Blue Grotto. (Beautiful). On our first dive we descended no sweat to the the Peace Rock about 55ft at a leisurely rate. We were about to run the line to the bottom (I had a lite)but I decided to check our pressures to be safe. She was at 600 I was at 1800. I should have known then she was an air hog but he heinsight is 20 20. I decided we needed to make our turn obviously and do our safety stop. I should mention I run a mares puck. We slowly ascended. I watched the bar graph to make sure we didn't come up too fast. Completed our deco and surfaced.

After our 90 min surface interval we made our second dive. I made several OK checks with her and when we hit the 60 foot mark about to make our descent down the line she said she was not ok. She seemed to be sinking so i grabbed her by the bicep and made a slow ascent. The I realized she had her hand on her power inflator. I stopped her and pulled the inflator from her hand and made her release it I then motioned to her to not touch that damn thing. She seemed a bit better and we made a full safety stop and then ascended to the surface.

On the surface I asked what happened and she said "she felt clostrophobic" I didn't flame her and told her it was ok. She asked if I want to go back down and dive a bit more I said I didn't think it would be good to bounce dive.

My question is. Would it be a bad idea to go back down to say 25 feet and dive a bit more or is it bad practice? Once you surface the dive is always over?

 

[boulderjohn]

My question is. Would it be a bad idea to go back down to say 25 feet and dive a bit more or is it bad practice? Once you surface the dive is always over?

In the PADI course that features using the dive tables, the students have to do problems using the tables to compute dive plans. In one of the problems, they ask the students to compute the minimum surface interval between two dives. On the imperial version of the question, the correct answer is 4 minutes. In the metric version, it is 0 minutes.

If you are using tables, the tables will tell you how long you stay at whatever depth following your previous dives and surface intervals. If you are using a computer, it will do the same thing in its dive planning mode. If they tell you it is safe to do a dive to a specific depth for a specific amount of time, go for it.

Since you don't provide a lot of detailed about the dives, I can only guess. Going by what you wrote, if you were using a computer to guide that projected 3rd dive at 25 feet, the computer would have allowed you maybe 3-4 hours at that depth. Maybe more.

 

[Ephesmax]

Thank you for the reply mod. In a semi related question. Obviously heeding the display on my puck. We couldn't find the hole the first dive at 60ft. Would it have been bad to after the say a 60 min surface interval to make a second dive to the deeper depth of 100feet. Granted the bottom time would have only been 9min. Based off of my dive table. Do you always have to do the deepest dive first?

 

[Doc]

Thank you for the reply mod.

Boulderjohn transcends labeling as a MOD. He gives reasoned answers based on real life experience.

Don't get immersed in the mechanical/technical aspects, consider the psychological element:

I would have told her to sit on the blanket over here with me and let's watch other folks dive-in. We'll come back next week. Claustrophobia, if that's what was really going on, shouldn't be a revisited stimulus within that same day. This stuff takes time.

 

[Steve_C]

It is standard practice in the Florida Keys on the reefs for the boat to tell you that if you get lost to surface, locate the boat, and time and air and NDL permitting to continue the dive. So a dive need not end.

Being an air hog is some times a sign of nervousness.

It is my personal feeling, and I have never dove Blue Grotto, but if I had a diver go through air that fast I would not be taking them deep in a confined setting again and it sounds like you are diving deep.

 

[Doctorfish]

I always assumed that if you went back down without a surface interval, it should be considered a continuation of the original dive.

 

[boulderjohn]

Thank you for the reply mod. In a semi related question. Obviously heeding the display on my puck. We couldn't find the hole the first dive at 60ft. Would it have been bad to after the say a 60 min surface interval to make a second dive to the deeper depth of 100feet. Granted the bottom time would have only been 9min. Based off of my dive table. Do you always have to do the deepest dive first?

Excellent question.

Nearly 15 years ago, a conference of diving experts was convened on this very question. The first question they wanted to answer was where the rule that the deepest dive must be done first came from, and the second question that wanted to answer was why that rule exists. PADI representatives were part of the conference, and it was determined that the earliest reference to this rule was a suggestion in a 1972 PADI OW manual. No one from PADI knew who added that suggestion to the manual or why it was added. In subsequent editions, the wording grew stronger and stronger until it became a rule, and no one knew why. In the meantime, other agencies had picked up the rule until it became standard.

The conference concluded that there was no reason for that rule in standard recreational diving, but they maintained the recommendation for technical diving at the request of Dr. Bruce Weinke, based on his theory that bubbles produced on the first dive would be crushed to the point that they would produce problems for reasons that are not necessary in this discussion.

In past discussions on this topic, people have generally agreed that there is a practical reason to do the deepest dive first. If you are using tables to guide your diving, if you do the deeper dive first, the required surface interval before the second dive will be shorter, sometimes significantly so. Those who still know how to use tables can check this and see. That is the only known reason--to get into the water for the second dive sooner.

In short, if you have had enough of a surface interval to do the planned second dive, there is no safety-related reason not to do that dive, even if it is deeper than the first one.

 

[TSandM]

I believe the Smithsonian conference also recommended that the second dive be within 40 feet in depth of the first one. It wasn't carte blanche to do a much deeper dive second, although they did not have data to explain why the recommendation was made, except that the dives they analyzed which were completed safely fell within those parameters.

I do disagree that the day should have ended because the diver complained of claustrophobia. It is not at all unheard of for someone to have an experience or a reaction that they don't cope well with, but after reflection and reassurance, they go back down and cope fine. (I see this all the time in OW dives.). It is a judgment call on the part of the diver and her buddy, as to whether her degree of anxiety is sufficiently worrisome to make further diving risky or counterproductive.

 

[tursiops]

OP, let me see if I've got this straight. You are a new diver, presumably only OW certified, and your dive plan was to exceed 60 ft into an overhead environment, which you feel is OK because you have a light. And your buddy is a nervous air hog. Your question is about surface intervals.

You asked the wrong question. Your question should have been, "Should I be doing this dive at all?"
And the answer is No.
You need more experience, more training, more awareness of what can go wrong.
Reading books over the winter is NOT the way to get experience or training!

I'm afraid you don't know what you don't know, and are dangerously overconfident.
See https://en.wikipedia.org/wiki/Dunning–Kruger_effect.

 

[Doppler]

The "hole" at the back of Blue Grotto is a cave... not a cavern because there is no light back there... and one light between two divers is a very poor choice.

Suggest you add this to your reading list. https://decodoppler.wordpress.com/2012/08/14/an-open-letter-to-new-divers-about-staying-alive/

While you are there, you might also take the time to read this one too...\\https://decodoppler.wordpress.com/2015/03/04/normalization-of-deviance/