Fresh water diving - Question

[Doc Intrepid]

GUYS,

I sincerely appreacite your concerns but please give me a break. I told you that's the reason why I joined the club. I got my OWD during the summer holiday and you probably know what the OWD course in the holiday resort looks like. I said, three times already, I understand there's alot I need to learn.

Hi Mirjana,

(And welcome to the board...)

check out this website re: high altitude diving:
http://www.mindspring.com/~divegeek/altitude.htm

It explains how to determine "actual" depths in high mountain lakes, for your dive planning.

It sounds like you are an ambitious new diver and I think that by getting with a club you have made the right choice. There are undoubtedly people in your club who can sit down with you during the evenings and go over dive planning in detail. If they are like people in my club, they ENJOY doing things like this with new divers!!

The most important thing for you to realize is something you seem to already know - that there is a lot your open water course didn't go over completely.

The second most important thing for you to realize is that it is important for you to plan your own dives. Plan them with the club, by all means. Dive with the club. But make sure you sit down with the club members who are planning the dives, and understand how they are planning them - air consumption rates, how long, how deep, contingency planning, etc.

Don't do any more "trust-me" dives. Sounds like you'll do fine. Have fun!

Regards,

Doc

 

[divenut2001]

As Desa pointed out an "SI" is a "surface interval". When you arrive at alttitude you have technically just surfaced and must do a surface interval, 2 hr min.

Your LDS (local dive shop ) should have altitude conversion charts and most likely offers Altitude Certifications. Padi uses the altitude section from the AOW manual which also has the altitude conversion charts printed in them. You should also take the nitrox course if you plan on diving @ altitude. You can take them both at the same time if you wish.

Contrary to "Aquamaster's" comments "no, the sky is not falling", but I speak from the facts which I only became aware of myself when I took my Altitude Cert up in Lake Tahoe, Ca El= 6,224 ft or 1897 m. I and everyone else for that matter who were taking the course were shocked to learn of how many diver deaths there were up there. I can't remember the exact number, but it was enough to get our attention. As long as you are aware of the dangers and are "properly" trained it should be "no problem".

One of the dangers that was not mentioned in the book and I don't know why, is the danger of "over weighting". Because you are @ altitude where the air is thinner, if you're too over weighted, you may not be able to put enough air in your BC to "stop" your descent. Also "ascents" should be even slower and safety stops shallower @ altitude then @ sea level.

You're a new diver and I'm sure you'll do fine. As others have said, stay away from the "trust me" dives. Make sure you can plan your own dives and understand them. A computer is a good investment but make sure you read and understand the owner's manual thoroughlly and know what your computer is telling you. All too often I've seen new divers with a brand new out of the box computer, trying to figure out their computer just before the dive. Have fun and dive safe...

 

[DEEPLOU]

Aside from the issue of atlitude diving that has been addressed, I have noticed that several posters seem to have forgotten the true definition of "bottom time".

They look at their computer when they surface and see 45 min or what ever, and then say that was their bottom time!

Bottom time is from leaving surface to leaving the bottom, not leaving the surface to arriving at the surface, (what I call "run time")

 

[Warren_L]

GUYS,

I sincerely appreacite your concerns but please give me a break. I told you that's the reason why I joined the club. I got my OWD during the summer holiday and you probably know what the OWD course in the holiday resort looks like. I said, three times already, I understand there's alot I need to learn.

Hi Mirjana - I apologize if I sounded like I was getting on your case. Really, the advice, as with everyone here, is intended to make sure you understand how critical it is that you undertake the proper planning procedures to keep you safe. It seems that you certainly do. If you have any questions, we're all here to help.

Cheers & safe dives,

Warren

 

[lostinspace]

Hi Mrijana - very glad to hear you're ok. Sorry for the delay in response, a power surge from a tropical thunderstorm fried my modem!
I suggested you go see a doctor because according to my (conservative) BSAC tables for the altitude difference you made & the dive depth & dive time (DT to me means time on leaving surface to reaching 6m safety or decompression depth whatever comes first) you moved from tissue code A to B on reaching altitude, and then spent quite a bit of time at depth, raising your tissue code to G and necessitating decompression stops.
It is quite likely your dive guide took you through a multi-level computer-aided dive plan that accounted for all of this, and you would not have noticed.
As suggested by others, spend some time chatting with more experienced divers, and spend some time learning how to use tables so that you can understand the dive plans.
Always try to rent or borrow (or even buy) a computer so you yourself can keep an eye on your depths & times.
Again, glad to hear you're ok.
lostinspace

 

[Mirjana]

Sorry for not being able to respond earlier, I was out of town for couple of days. We did a local night dive (only 10m, but visibility was 0) in the mean time. I cannot believe I have not discovered diving before

Thank you all so much for all of your response. I look forward to learn some of those stuff so that I can actually talk about the dive planning, altitude training and all of that, and to be able to ask right question. It is really amazing that you all came back with so many good responses and so much useful information. This is a great support for beginners like myself

HUUUUUGE THANKS!!!!!

 

[DepartureDiver]

One of the dangers that was not mentioned in the book and I don't know why, is the danger of "over weighting". Because you are @ altitude where the air is thinner, if you're too over weighted, you may not be able to put enough air in your BC to "stop" your descent. Also "ascents" should be even slower and safety stops shallower @ altitude then @ sea level.

The overweighting issue is because of the dive being in fresh water, although the amount of any overweighting would be relatively small. If using a weight suit versus a dry suit, there is also some expansion in the neoprene at altitude so the overwieghting issue would be even less. The actual difference in air pressure is small and the issue of not being able to put air in a BCD to slow an ascent is a myth. It is really just an issue of being slightly overweighted ... but if you are already overweighted at sea level, it becomes even more so at altitude. As to the ascent rates, any slow ascent rate is equally as good at sea level as it is at altitude ... just don't be doing 60'/min ascent rates at sea level or altitude. An ascent rate of 30'/min is nice at altitude, but I personally prefer to slow them down a little more ... even at sea level. Also, safety stops should not really be made shallower. Doing stops under pressure can be good. In general, the 15' safety stop is too shallow even at sea level (depending on the dive done of course). Do the normal deep safety stops as you surface - which work great at altitude also. Calculate these based on your actual depth (i.e. first stop at one half of your deepest depth) and work your way towards the surface.

I'm sure the profile in question was really a good multi-level dive, but make sure you take time to properly plan all your dives since your dive buddies may not alwaysk now what they are doing or may mess up the planning. If the entire dive was spent at 23 meters, decompresson was absolutely required ... and I would have recommended the first stop being at 12 meters.