sea saw profiles

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buleetu

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Location
ireland
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hi all

i was out this morning on a dive with 3 others and a guide

i had my camera along and my buddy and i agreed on 25 m max depth for anything special and 20 m for crusing along, we met with a neopolean wrasse and we followed her down to 25m to try get some pics then she went deeper and we ascended back to 20 m then i seen a nudi and ascended up to 18 or so for a few shots with my buddy at my side all the time, we then settled back to 20 metres and the neoplean came back so we went down again, never any more than 25 metres which was our max!!

after a perfect dive with a lovely hawksbill turtle at the end we all got on the boat and the guide ripped into me, she said we were see sawing like a mad people and would end up in a chamber if we kept it up and i was responsible because of my camera and the people who always end up in the chamber first are photographers and videographers because of the profiles we dive to get the best shots

we were not doing it constantly,we only done it twice, is this a dangerous practice like she suggests or is she overly conservative and just worried that she might be responsible or her comapany if anything goes wrong with me or my buddy??

thanks guys
 
Square profiles aren't always possible. I think she's overstating the case, especially given those depths (7m change).
 
Multi-level diving is not inherently more dangerous than single-level diving, but it depends on how you are managing your nitrogen absorption and decompression. If you are diving with computers, and you make sure that you never ascend more rapidly than the recommended rate, your computers should be able to deal with the multi-level dive. It is more difficult to calculate using tables, but the easy and conservative method is to assume that you spent the whole dive at the max depth.
 
im using a computer, and i ascend slowy and in control using my lungs or fins, my computer warns me if i go up too quick,and its only beeped once for going too fast and i realised right away and stopped, i think she was stressed out today or something like that maybe she was tired, fair enough if i was up and down from 30 metres to 20 back to 30 then up to 15 then back to 30 she would probably have a point but it was only a few metres 2 times during the dive
 
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Your guide flipped out over nothing. It's amazing how a little bit of knowledge turns into a nasty attitude in a hurry. You have nothing to worry about.

-Charles
 
Your guide maybe looking out for your best interest, but she sounds rather flaky to me.

PADI discourages going up, and down, but if one thinks about it why (assuming it is done slowly). There is nothing dangerous about doing a 30 minute dive at 60', and IMO it would be less dangerous to do 15 minutes at 60', 10 minutes at 40', and another 10 minutes back at 60'. It would actually be safer vs. the square profile.

Sounds like your guide was a bit bored that day, or maybe she was having some personal crisis, and needed to vent?
 
Well I do not know that the DM saw enough to "rip into you". I would probably not have gone down the second time, and in general try to stay shallow if my dive takes me there. In other words I would have stayed at 18m after my nudi encounter was over. But I have made dives similar to yours, for similar reasons, and never experienced any issues. Do try to limit yourself in general though. 7 meters is almost a full atmosphere, I try to keep my richter scale dives to 3 meters or less.

Computers are great tools, however you should be aware of their limitations. You computer can not take into account ANY physiological differences between you and the person the model was designed after. It also cannot tell you that you are more dehydrated, tired, and stressed today than yesterday. In other words, do not trust your computer completely. It is a guide, not a substitute for knowledge about nitrogen loading and off-gassing.

That all having been said, keeping hydrated, slow controlled depth changes and generally conservative profiles *should* make the odd dive survivable.
 
hi all

i was out this morning on a dive with 3 others and a guide

i had my camera along and my buddy and i agreed on 25 m max depth for anything special and 20 m for crusing along, we met with a neopolean wrasse and we followed her down to 25m to try get some pics then she went deeper and we ascended back to 20 m then i seen a nudi and ascended up to 18 or so for a few shots with my buddy at my side all the time, we then settled back to 20 metres and the neoplean came back so we went down again, never any more than 25 metres which was our max!!

after a perfect dive with a lovely hawksbill turtle at the end we all got on the boat and the guide ripped into me, she said we were see sawing like a mad people and would end up in a chamber if we kept it up and i was responsible because of my camera and the people who always end up in the chamber first are photographers and videographers because of the profiles we dive to get the best shots

we were not doing it constantly,we only done it twice, is this a dangerous practice like she suggests or is she overly conservative and just worried that she might be responsible or her comapany if anything goes wrong with me or my buddy??

thanks guys

Lets look at it with imperial numbers.
Level at 60 feet, then down to near 80 feet, back up to 60 feet, then up to 50 feet, back down to 60 feet. Makes it look a little more severe. Also, how fast were the ascents from 25 metres back to 20 metres, or from 20 metres up to the nudi at 18 metres?

Regardless of what the photographic subject matter is, the paramount importance is your own safety. Dive tables and dive computers were designed for dives of a single depth or for multi-levels beginning with the deepest part of the dive first and progressive ascents.

Just because you have done sawtooth profile dives in the past with no ill effects, doesn't mean that you aren't exposing yourself to excessive Nitrogen loading in certain tissue compartments.
DCS/DCI is not just some strange condition that newbies and divers with poor control get. Its a serious, extremely painful, life threatening, and certainly life altering incident/injury. The next great photograph is not worth paralysis or worse.
Check out the latest issue of DAN Alert Diver magazine. There are a couple of articles about very experienced IMAX photographers taking serious DCS hits, even with very disciplined profiles.
The DAN website also has some great information. The sight provides the opportunity to send a message with the above scenario to a DAN Doctor who could give advice based soley on statistics and research.
DAN Divers Alert Network

:coffee:
 
Lets look at it with imperial numbers.
Level at 60 feet, then down to near 80 feet, back up to 60 feet, then up to 50 feet, back down to 60 feet. Makes it look a little more severe.

Switching unit systems so the numbers are greater somehow magnifies the supposed risk of profile? No. The profile is the same regardless of what units you use.

IMO, sawtooth profiles aren't inherently dangerous. True: it's simpler to consider a dive where the fast tissues are only loaded at the start and are in decompression throughout the remainder of the dive. But what happens on the bottom is just a small part of the DCS equation. The paramount concern is how you ascend.
 
Do a really slow ascent and add a couple minutes to your 5m safety stop if you're worried. Some computers (Sunntos...) do that for you if they detect that kind of profile.

That said, your guide is somewhat responsible for your safety underwater. And not everyone has a computer. Four people spread between 18 and 25 meters are a lot harder to keep track off than a single line of divers, and might end up with completely different deco profiles. Also if the guide is at 25m and you're at 18m, there is absolutely nothing he can do if you freak out (you won't, but he doesn't know that) - or anything else happen - and he's probably stressing about it. Please be considerate!

(That's one reason I don't like to dive within a guided group - I like to set my own pace).
 

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