Pre Dive Procedures
There are a couple of things we should do before starting the dive.
Similar to a flight crew we want to make sure all systems are go and that everything is working and we want to make sure we have not forgotten anything.
In recreational diving we are taught to do a buddy check and this is something along that line just a little bit more in depth.
The procedures below should also be very similar, if not identical, to what you would encounter during any DIR class.
Most cave training agencies also follows a similar protocol.
The purpose of these procedures is to make sure everything is ok before we start the dive.
Some of them also doubles as training aids
because they make you practice things like air sharing and valve shutdowns.
Things that seldom happens during the dive but when it does it is serious.
And of course we want to be prepared for the worst scenario.
- Equipment check
- Bubble check
- Valve Drill
- Dive Plan Review
This is usually done as a matching drill where the one who is leading the dive
will go over his equipment from top to toe. Everybody checks their own equipment and confirms "check" to the dive team.
When possible you should do this in the water at the surface but if that isn't practical you can do it on land instead.
Something I generally started to use more and more are check lists.
I write them down in my wetnotes, usually on the last pages to keep the first pages empty for communication during the dive.
The reason to use check lists is to lower the taskloading and there is not a chance that you will forget something.
So even if you know everything (and you should) you can quickly work your way down the list and know you have everything.
Here is an example for a deco dive in the ocean.
|Longhose||breath longhose u/w
|Backup reg||breath backup u/w
|Wing inflator||inflate wing
|Wing deflate||deflate wing
|Wing pull dump||confirm lower pull dump is working
|Drysuit inflator||inflate drysuit
|Drysuit exhaust valve||deflate drysuit, check that it is open
|Argon bottle||confirm that the valve is open
|Primary light||confirm that it is deployed and working
|Left backup light||confirm that you have it||deploy, check it and stow
|Right backup light||confirm that you have it||deploy, check it and stow
|Bottomtimer||check that you have it and it's working
|Compass||check that you have it and it's working
|Additional instruments||watches etc.
|Knife||confirm that you have it||deploy, check it and stow
|Scissors||confirm that you have it||pull it out, check it and put back
|Safety spool||confirm that you have it||pull it out, check it and put back
|Lift bag/surface marker||confirm that you have it||pull it out, check it and put back
|Backup mask||confirm if you have it||pull it out, check it and put back
|Wetnotes||confirm that you have them||pull it out, check it and put back
|Additional items in pocket||More spools etc?
|Stage bottles||confirm what you have
|Deco bottles||confirm what you have
|Additional items||Reels etc.
If you like you could add thing like mask, fins, gloves, hoods.
Usually you would not forget them but if you had a walk before hittting the water it might be a good idea.
And remember that these lists can be modified for different dive scenarios - see them as a work in progress.
Anything you want to add, just put it there.
The purpose of the bubble check is to make sure you do not have any leaks or problems even before the dive.
Dip down under water and have your buddies check you for leaks.
You want to specifically look for leaks around first stages, second stages, hoses, SPG etc.
At the same time you can take a quick look at your buddies hoses and equipment in general to just confirm everything looks ok.
S-drill is short for safety drill.
It's basically a drill to make sure you can share gas and that your long hose is deployable and not stuck behind other hoses or things.
In a modified S-drill you just deploy your longhose to make sure it's free.
In a full S-Drill you drop down to 3m/10 feet or so and perform a simulated out of gas scenarios so that everybody get some practice at sharing gas.
In short the procedure is this:
- Face team mate with some distance apart
- One diver signals out of gas (rapid light movement)
- The other diver donates his longhose while they they swim towards each other
- Make sure the out of gas diver gets gas
- Confirm that the OOG diver is ok (with an "ok" signal)
- Make sure the light cord is free from the longhose
- Deploy full length of the longhose
- Check that the longhose on the OOG diver is clipped of to his d-ring
- Go into touch contact and swim a couple of meters/feet.
- Make sure to manage the long hose so that it can't get entangled in anyting
- Stop and put everything back to normal
The important thing is for the gas donor to take control of the situation and make sure his buddy is ok before proceeding.
Besides doing it properly instructors are also checking that you can keep your trim horisontal and that you have control over
The purpose of the valve drill is to make sure your valves are in the right position (fully open) and that you can open and close them while in control.
This is also doubles as practice drill just like the S-drill.
In it's modified form you just reach back and check that your valves are fully open.
A full valve drill is performed one at a time while the buddy is supervising.
The procedure is:
- Shutdown right post and switch to backup reg
- Open right post
- Close isolator and open it again
- Shutdown left post and switch back to longhose
- Open left post
- Make sure all valves are open
- Give buddy an OK when you are done
As always when you are not breathing the longhose you clip it of to the right d-ring.
Unless you are very comfortable with this exercise I suggest unclipping the longhose before closing your left post.
Also when you have a problem it is important to depressurize the regs if you are trying to troubleshoot a small leak
as it will continue to leak even after you have shut down the post.
So current procedure is to breath down the reg before switching.
To make this drill even more realistic you could also signal you buddy while you shut down a valve (attention signal).
That is what is going to happen if you have a problem during the dive and you want to make sure you get his attention.
If you do that during the drill it is more likely you will do it in real life too.
It's also a good reminder that you need to keep looking straight ahead and not down.
Looking down will only make you unaware of your environment, buoyancy and buddies so try to keep that head up.
You also need to have your primary light on in your hand but switch it to the hand not turning valves.
In real life you need to be able to reach back and check your valves anytime during the dive without alerting your buddies.
And of course during training your instructors are looking for you to do this while hovering completely stationary (not swimming around)
in horizontal trim with good bouyancy.
Dive Plan Review
Dive plan review is when we repeat our dive plan to make sure everybody understands what we are going to do,
how much gas we are going to use, our maximum depth, how much deco etc.
After we done the S-drills and valve drills we pop back up and go over this before commencing with the dive.
To have some kind of structure you can use the SADDDDD. (Nice acronym huh?)
- S - Sequence
- A - Air
- D - Depth
- D - Direction
- D - Distance
- D - Duration
- D - Deco
S stands for Sequence, which means in what order are we going to dive and also how the dive will proceed.
For instance Bob will lead the dive, followed by Andy in second and Sue in third position.
Our plan is to dive the wreck, find the bell if possible and then return to the upline.
A is Air which in our case means breathing gas.
So here we defined how much gas we will use, how much will be our reserve gas and when we will turn the dive.
During this we also check our pressure gauges to make any adjustments. For example we will use one third of our gas supply for this dive going in and one third coming out.
Vicky has 3300 psi so a third is 1100 psi. John has only 3200 psi so a third is 1000 psi and that is what they will use.
That gives Vicky a turning pressure of 3300-1000 = 2300 psi and John will turn the dive when he hits 3200-1000 = 2200 psi.
D is for Depth. For example in this lake the maximum depth is 30 meter.
Since we want to check out some of the overhangs we will stay at about 25 meter which will also probably be our average depth.
D for Direction. For example drop down from the dive boat and take a SSW heading and follow the reef.
D for Distance. For example during this cave dive we could probably reach 2200 feet on our penetration gas but at 1500 ft we will encounter a major restriction so we will turn the dive there.
D for Duration. Since we did about 30 minutes of bottom on our last dive and we will stay shallower on this one we will probably do about 40 minutes on this one.
D for Deco. Given that we should do an bottom time of about 40 minutes our deco should stay within the minimum deco limits so we will just do a minimum deco ascent.
Sometimes it not possible for us to do everything on the surface before continuing the dive.
For instance diving from boats with currents on the surface you are better of doing your equipment check and dive plan review on the boat,
jump in and drop down to 6m/20ft were the current is less and do bubble check, modified s-drill and modified valve drill there
before proceeding down.
No matter what conditions we are diving in we can always make the best of it if we know why we do the pre dive procedures.
If you never practice s-drills and valve drills you can't do it when you have to. It is that simple.
And if you dive with somebody new it's nice to know they can share gas or shut down their valves, don't you think?