Turning a dive

There has been a lot of talk about proper dive planning, gas management, etc. and how it applies to knowing when a dive is over. For the sake of this discussion I'm talking about either turning the dive on an out and back, or ascending for a drift dive. Some things that come easily to mind are: the plan says it over, running out of NDL time on the computer, low gas, mission accomplished.

What factors do you take into consideration when you decide the dive is over?

All of those are good. I'd add that the management of them is the key.
Monitoring air consumption, depth, temperature, etc. regularly and processing all the other factors you mentioned into an ajustment to the plan. Hell - that should be a part of any plan... "let's re-evaluate at points X, Y, Z..."
Also consider what the rest of the diving day will be like. Planned SIT times, activity levels, any recent changes in health, all these factors as it realtes to my buddy, etc.

Which is usually spearing fish or hunting lobster.

If there are no fish, there is no reason to keep taking on N2. Cuts down on the SI while we head to a (hopefully) more productive location.

Apart from just when the plan says the dive's over
- Possible unexpected weather conditions or currents that come from nowhere
- Another fairly common one is cold - sometimes someone makes a change in gear, or if there's someone wearing a rental suit etc - if they get too cold I turn the dive.

The cold plays a large factor for turning a dive. Also poor visibility and poor navigation.

Last weekend we went out for a dive, the report from the day before was great vis and most likely another 4 - 5 days of diving before the water would be like soup. From our vantage point we could see a couple of kms across the lake to the mouth of the river feeding the silt into the lake. You could see the crescent shaped border of silt as it entered and would eventually, slowly move out to consume the entire lake.

The silt cloud was about 600m to the north of our dive site so we thought it would be okay for the dive and in we went. We had about a 600 m swim/navigate to the site, which is not to difficult if you can find the road that would take us to the dive site. Yes a road, the dive site is a submerged town site behind a dam.

We found the road and were making our way to the site (so we thought) but not relying on the compass heading and trying to rely on instinct we turn left when we should have turned right. We finned along watching the boiling silt cloud to our right thinking that is where our goal is and that is where we need to be. After some head scratching we called the dive.

We surfaced from 7 m (20') to discuss the silt cloud and the fact that we turned left when we should have turned right. Oh well, with a renewed faith in our compass we descended. By now the silt cloud was all around us, it had moved across the lake at an unbelievable rate. I was going down in zero vis, I held my computer up to my mask, hit the back light button but couldn't make out the reading. This silt is thick. "I wonder if it will clear up as I descend" I was thinking as my fins touched bottom in the 7m of water. I found the answer to my question and started my ascent. I surfaced the same time as my buddy about a foot away from him. Spitting our regs out we both laughed about the conditions, Mexman figured the vis was -5 feet. So we called the dive - again.

another one that is harder to pin down and must be agreed upon in the pre-dive planning phase or it will be hard to pull off:

When you feel uneasy (unless of course you are always uneasy.)

If for any reason I start to feel uneasy I will turn the dive. I don't remember putting this into play yet but I am psychologically prepared to do so... and I want my buddy to be ready to call a dive for that reason as well.

Not to be spooky here but I think that we have senses we need to listen to that don't always make it to the congitive level.

Related to the uneasiness: the task loading and escalating events scenario. If enough little things go wrong, one more could cause major uneasiness if not an actual problem. I guess if you're thinking, if one other thing went wrong now I would not be happy at all - it's time to just avoid that and turn the dive.

A major reason to turn the dive is if a failure has occured that makes continuing unsafe or unwise. In this case you have to evaluate the dive, and take the proper action. For example, if you are diving doubles and your primary freeflows, and you've shut it off. You see that you still have a fair amount of gas, so you decide to navigate to the exit point, rather than making a blue water ascent. It's important to know when to turn a dive, and when to call a dive.

If something goes slightly wrong and it's not cause for turning or calling the dive, I think that the buddy should always be alerted to what is going on. Don't take a chance, take out the wetnotes and write it down.

We had two local incidents where the divers thought their buddies had understood the problem, when in fact they hadn't.

biscuit7 once bubbled...
What factors do you take into consideration when you decide the dive is over?

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Heh, don't forget boredom!

Bored? Then it's time to head up. It is _recreational_ diving, after all

Anyone can turn the dive for any reason at any time without any pressure.

Anyone actually turned a dive because they are bored?