Decompression diving

ericg753 · Mar 24, 2014

Hi everyone,

Introduced myself a month ago in the Intros section of the forum, still very new to diving and just did my first 2 dives in WPB (60 feet). Traveling to the Cayman Islands beginning of April, my scuba instructor told me we are doing 100 foot dives this time. Very tiny bit nervous as this is still new, need to understand if this is considered a decompression dive? Please bare with me, got certified last November and did the online course in September, trying to recall what I learned.

Far from becoming advanced (for Nitrox usage), so will be using air. What is considered decompression diving and should I be worried, at 100 foot depth, of having to make all those stops? My instructor will be my guide, I know he's going to answer all this for me but I'm trying to plan ahead of time.

Thanks for your patience, everyone. Got to say I'm very happy I took up scuba diving, looking forward to meeting new people and diving in many places!

Eric

Agility · Mar 24, 2014

For recreational diving you do not have to make "all those stops" if you do not exceed your NDL, a controlled ascent and a safety stop at 5m (15ft) for 3-5 minutes are recommended. Although all dives include compression and decompression the term decompression stop is use for a mandatory stop during ascent, that has to be inserted to let accumulated inert gas escape from your body.
Your dive tables or the planning function of your dive computer will tell you how long you can stay at your planned depth and ascend to the suface without needing theese mandatory stops, this time is called NDL (no decompression limit). Practically all dive computers show you how much time you have left before you exeed NDL.

ericg753 · Mar 24, 2014

Agility,

Thank you for your reply. After I posted (haven't been on a forum in years) I THEN started reading other similar posts from "dive newbies" like myself. Got my answer, thank you

rivers · Mar 24, 2014

Also, if you're not comfortable diving to 100 feet, then don't. Tell your instructor you're not comfortable. If he doesn't listen, thumb the dive. You're in charge of your own diving, not him.

hroark2112 · Mar 24, 2014

It's never too early to get certified in nitrox. Just get certified and learn how to use your computer properly.

Dive safely and have fun!!

Mustard Dave · Mar 24, 2014

ericg753:
Hi everyone,

Introduced myself a month ago in the Intros section of the forum, still very new to diving and just did my first 2 dives in WPB (60 feet). Traveling to the Cayman Islands beginning of April, my scuba instructor told me we are doing 100 foot dives this time. Very tiny bit nervous as this is still new, need to understand if this is considered a decompression dive? Please bare with me, got certified last November and did the online course in September, trying to recall what I learned.

Far from becoming advanced (for Nitrox usage), so will be using air. What is considered decompression diving and should I be worried, at 100 foot depth, of having to make all those stops? My instructor will be my guide, I know he's going to answer all this for me but I'm trying to plan ahead of time.

Thanks for your patience, everyone. Got to say I'm very happy I took up scuba diving, looking forward to meeting new people and diving in many places!

Eric

That sort of depth is too much for a new diver. Under the PADI system, an Open Water diver is certified to 18m/60 feet, so you will need your Advanced Open Water (or other agency equivalent to dive to this depth). This sort of depth isn't difficult to dive to, but you should build up your depth gradually so as to polish your skills and gain confidence.

From the PADI recreational dive planner tables, you will have 20 minutes no-decompression time at 30m/100 feet. Using EANx 32, that increases to 30 minutes. The nitrox course can be done in the classroom and is well worth considering for 30m/100 feet dives.

All dives are decompression dives, as a fast ascent can get you bent, but we refer to dives where no mandatory decompression stops are required as within no-decompression limits. Most agencies consider dives requiring mandatory decompression stops outside the limits of the recreational diver.

flots am · Mar 24, 2014

ericg753:
Introduced myself a month ago in the Intros section of the forum, still very new to diving and just did my first 2 dives in WPB (60 feet). Traveling to the Cayman Islands beginning of April, my scuba instructor told me we are doing 100 foot dives this time. Very tiny bit nervous as this is still new, need to understand if this is considered a decompression dive? Please bare with me, got certified last November and did the online course in September, trying to recall what I learned.

Congratulations on being nervous! It's your brain trying to keep you alive.

You are not remotely qualified for this dive, regardless of what anybody tells you. When you go to the Caymans, before you pay for the dives, tell the instructor you will not be doing any 100' dives and would like him to take you to a nice shallow reef. If he gives you a hard time, feel free to show him my patented "You're #1" hand signal and walk out the door.

Stay shallow and easy. You'll have a great time, wonderful dives and will live to see another day.

Aside from anything else, a shallow reef dive will probably get you nearly an hour on a tank, while a 100' dive will get you maybe 15 minutes before you're low enough on air that you need to start surfacing.

flots.

diver 85 · Mar 24, 2014

Understand your concerns-----but------IMO, you need to retake (?some of)your training, ie too many unanswered questions--& stay off that #$%#^& computer.

............You're supposed to be a certified diver now----stop & think about that statement for a while(hint---you're responsible for YOUR diving)...........

KeithG · Mar 25, 2014

diver 85:
Understand your concerns-----but------IMO, you need to retake (?some of)your training, ie too many unanswered questions--& stay off that #$%#^& computer.............You're supposed to be a certified diver now----stop & think about that statement for a while(hint---you're responsible for YOUR diving)...........

Eric: my interpretation of the above response (which I agree with) is...
There are many threads moaning about how poorly trained divers are these days. How they do not understand NDL concepts and simply ride their computers. Your question seems to reflect this.

As a certified diver (I assume OW), you should have been able to answer your own question. I do not claim that you should have known the answer, but you should know how to determine the answer based upon your very recent training. In the old days it would take you 10 seconds to check your tables to get the answer.

---------- Post added March 25th, 2014 at 10:50 PM ----------

P.s. have fun & make sure you keep lernin.

Mr Carcharodon · Mar 26, 2014

Well decompression diving is diving outside the limits set by your computer or tables. You might be surprised to find out how arbitrary and flexible those limits are. It is really useful to have some rule of thumb to let you know if you are close to the limits. There is the 120 rule. If you find an old set of the US Navy tables you will find that the sum of your depth and bottom time is 120 for many depth time ranges. Now that may be considered overly aggressive by today's standards so you may want to consider shaving off 5 or 10 from your sum. If you do so you will be fairly consistent with the DSAT tables. Do understand that if you are cold, or did a lot of work on a dive, or felt bad going into the dive, you should really dial back your limits by 5 or 10 minutes more or wait until the next day. Being in tune with yourself is more useful than using a one size fits all tool.

Diving is great and there is so much to see out there. Go slow and you will be fine.

Decompression diving

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