I can't answer this.

[Wijbrandus]

My wife and I are planning our next trip. During our last trip we had very rough surface conditions, and both of us fed the fishes. We got ill waiting for the boat to arrive as we bounced through the waves.

So last night she asks me how we could avoid getting seasick in this situation. I say well, we could spend a little money and get a spool for our sausages, launch it from fifteen feet, and hang out until the boat arrives. I figure if she goes for this, I get to spend money at the LDS for a couple of spools.

Now she says that sounds good (woot get to buy diving stuff). She thinks about it for a few minutes, and then says, won't that be increasing our bottom time? Won't we go over our NDL? After all, any dives are planned out to a minimum of 35', right?

Hmm. Sounds right. But then I've got the answer for this one. No, it's just an extended safety stop. We'll be fine.

Ok, she says, how deep can you do your safety stop in a recreational setting and it still be considered a safety stop and not a multilevel dive? (Ok, now she's getting smart with me. Not a good sign.)

I don't know the answer to this, so I say, we'll just stick to the fifteen feet, and hope the wave action isn't hitting us there.

So then she asks me how deep do you have to be before this becomes an issue? For example, say the tables gives you 4 hours of NDL time at 35'. If I spent 5 hours on surface supplied air at 15' working on a dock, do I need to worry about some sort of deco?

Help. She's become way way too smart for my own good.

 

[O2BBubbleFree]

Are you asking a NDL question, or how to get a dumber wife? ;^)

 

[DBailey]

The textbook answer refers back to how bottom time is defined:

Your bottom time is the elapsed time from when you start your descent to the time that you start your direct ascent to the surface.

Time spent at a safety stop is not considered part of your bottom time. Think back to the diagram that is used to show the dive profile, the safety stop line was after the bottom time line.

 

[MikeFerrara]

The safest thing to do is to go through the multilevel planning and see for yourself. There are some things that you should know intuitively...and I think this is one of them.

 

[jonnythan]

Have you guys tried Bonine? I tried it recently and it worked wonders. Took one the night before and one the morning of the trip.

 

[simbrooks]

Two points to address here - first the boat/sausage thing. My concern is that although the boat might like to use your sausage as a reference point to know where you are, how are they going to know when you are ready to come up, or how would you know they are ready to pick you up. They arent going to come close up with engines running unless they know where you are on the surface. You are going to have to have some time on the surface, but there are a few if's in that whole scenario. What is probably making you sick is swallowing of water (keep your reg in if thats a problem) more than being gently jostled by the waves - if its stupidly rough, what are you doing out there and you are most likely not going to get seen by the boat even with a 6ft sausage or its going to be a tough pick up!!

Second - I think the post was mostly about NDL's and shallow depths. Although not fully versed on them in minutia, i believe you can hang at 15-20ft or less all day with no residual effects as long as you come up slowly. There is just over half an atmosphere difference between 15 and 35 ft and you can see that the numbers increase exponentially as they get towards 35ft, so they would continue off in that same fashion as you got shallower.

As for safety stops, they are an opportunity to do several things including offgassing and pausing to keep control over your ascent rate. There are some that advocate a single 1 min deep stop at half your depth followed by a safety stop and others that take a more deco like ascent profile of a min or 2 every 10ft from anywhere from 50-80% of your max depth all the way up and dont include more than a minute or two at 15ft or so. The safety stop(s) offer you a chance to get rid of some of the N2 that has been coming out of your tissues, you have moved up the water column fairly quickly (max 30fpm) and so there is a partial pressure difference between the gas that is coming out of your tissues and the gas you are breathing at the shallower depth, making stops helps to keep this pressure difference (gradient) at a lower value and allow the gas to be given off at a more reasonable rate than shooting to 15ft and hanging out for a while. These stops are better for your off-gassing and your body than just heading to the surface with no stops of course. I dont know if i explained that clearly, i am still a student of this myself (i have a few books coming for xmas that should help a little more ).

 

[Mako Mark]

The only real way to cure seasickness is to hold on to a tree.

Unfortunately most people who are suffering from the malady do not appreciate this piece of advice..

 

[hermosadive]

Sea sickness: Take ginger tablets. Works for 2 friends who are compulsive barf'ers :yuck: One take them a hour or so before diving, the other takes them daily regardless. Both no longer get sick.

Sausage: Why do you own a sausage with out a spool or line? Are you going to inflate it and hold on to the stem?

 

[Doc Intrepid]

My wife and I are planning our next trip. During our last trip we had very rough surface conditions, and both of us fed the fishes. We got ill waiting for the boat to arrive as we bounced through the waves.

So last night she asks me how we could avoid getting seasick in this situation. I say well, we could spend a little money and get a spool for our sausages, launch it from fifteen feet, and hang out until the boat arrives. I figure if she goes for this, I get to spend money at the LDS for a couple of spools.

Now she says that sounds good (woot get to buy diving stuff). She thinks about it for a few minutes, and then says, won't that be increasing our bottom time? Won't we go over our NDL? After all, any dives are planned out to a minimum of 35', right?

Hmm. Sounds right. But then I've got the answer for this one. No, it's just an extended safety stop. We'll be fine.

Ok, she says, how deep can you do your safety stop in a recreational setting and it still be considered a safety stop and not a multilevel dive? (Ok, now she's getting smart with me. Not a good sign.)

I don't know the answer to this, so I say, we'll just stick to the fifteen feet, and hope the wave action isn't hitting us there.

So then she asks me how deep do you have to be before this becomes an issue? For example, say the tables gives you 4 hours of NDL time at 35'. If I spent 5 hours on surface supplied air at 15' working on a dock, do I need to worry about some sort of deco?

Help. She's become way way too smart for my own good.

Your wife was difficult as a child, right?

Decompression theory gets fairly complex, and there is a lot that isn't known. But 'fast tissue groups' ongas and offgas rapidly. In 15' of water you are not 'ongassing' rapidly enough to pose any difficulty in ascending from 15'. From a theoretical perspective, based on my understanding, your 'no-decompression time' at 10' or 15' is essentially open-ended. In reality, of course, you get cold. When I was stationed on Guam we used to go shell-hunting in 5-8 feet of water, the dives could last upward of 2.5 hours before we got cold - wearing a wetsuit. PADI actually has a textbook out on dive computers and decompression theory, a slim volume written without jargon, that explains the basics reasonably well. Hint: Christmas. Stocking Stuffer.

 

[Don Burke]

So then she asks me how deep do you have to be before this becomes an issue? For example, say the tables gives you 4 hours of NDL time at 35'. If I spent 5 hours on surface supplied air at 15' working on a dock, do I need to worry about some sort of deco?

I once spent the better part of an evening playing with the simulator software that came with my dive computer.

Oceanic seems to think you are unbendable on air at fourteen feet. It took a _really_ long time to get into required stops at twenty feet.

Assuming you can work out the issues others have raised, doing your safety stops and then waiting at ten feet would be viable.

For repetitive dives, you will need to somehow account for hanging at ten feet. It is not really bottom time, but it certainly is not surface time.