Do you remember when you did your PADI Open Water course and the instructor talked about how you could plan your dive? If you did your course within the last couple of years you most likely planned dive #4 of your Open Water course together with your dive buddy.
Do you still remember how to plan your dive and do you do it before every dive? Well – look no further, even though you remember you might be able to pick up a few tips by keep reading here.
You will learn different ways to plan your dive and what to be aware of on your dive profile while diving. You will also get some important information about your next dive – like if you can safely make a deeper dive after a shallow dive.
In this article you will learn about planning your dive based on how much nitrogen your body will absorb, so that you can make a safe dive.
Dive Your Dive Plan
Dive Site – Let’s start out by getting some facts ready about the dive site you are planning to dive….
- How deep is it?
- Does it have a sloping bottom?
- Does it have high rocks/corals sticking up from the bottom?
- Is it a wall dive?
- Or are you planning a wreck dive?
So what you basically need are….
- Your planned deepest depth.
- Are you planning a multilevel dive?
- What are your next level or two next levels.
- Find out how many minutes you are planning on staying at the different levels.
- Remember that the deeper you go – the more air you will be using.
- Do you already have nitrogen in your body from a previous dive?
Once you have this information, you are ready for the next step – planning the dive.
Traditionally you would plan your dive using the PADI RDP (recreational dive planner) which is based on years and years of experience and contain well proven safety limits of time and depth. In this day and age your easiest way of planning your dive is by either using your dive computers dive planning mode, or to use one of the many dive planning apps that you can download on your smartphone or tablet.
Dive computers are all calculating the no stop time (no decompression limit) via an algorithm, which is using the same parameters as the dive tables. You will get very close to the same no stop time as if you were using the PADI RDP or PADI e-RDP.
Remember you don’t want to dive to the limit, so always plan your dive so that you have a minimum of 5 minutes no stop time left at all time. If you’re planning a dive where you are staying more or less at the same depth, then your dive computer will be the easiest to use.
Most likely you’re dive computer has a program that runs on either Windows or Mac OS, where besides from downloading your actually dive profile you can also make a dive plan. This plan however is often based on your air consumption and is not always taking your nitrogen load into account.
If you want to make a multilevel dive then you could be looking at using a dive planning app, you can find several apps either on App Store or on Google Play. The dive apps are all based on one or more of the available dive tables and are therefore replicating them, so that you will get exactly the same results, as if you were to use the physical dive table.
If you are using an app to plan your dive and you are planning on doing a multilevel dive, then you will need to treat each level as a separate dive, as most apps are not able to plan for multilevel dives.
After you have planned your dive you want to dive your plan, here it is important to stick to what you have actually planned to stay well within the limits of your no stop time.
Your dive profile should ideally look something like this:
Here you are starting at the lowest point and gradually making your way up to more shallow depths.
There are several other forms of dive profiles that you should try to avoid, as they will increase your risks of decompression sickness, also known as DCS.
One of them is the ‘reverse profile’ this is where the diver starts shallow, and then at the end of his/her dive ends up at a deeper depth. This will load your body with extra nitrogen at the end of the dive, where we actually want the body to start off-loading nitrogen.
Another profile is the ‘sawtooth profile’ where the diver accidentally moves up and down from deep to shallow several times during his/her dive. This will also load the body up with more nitrogen and not give the body time to release nitrogen.
So always start your dive going to the deepest point first, and then slowly making your way shallower. This way you will be more safe and decrease the risks of DCS. If you are interested in reading more about the different dive profiles, here is the link to the Wikipedia page about reverse profiles etc.
Just to finish off let’s talk a little bit about your next dive. Many divers are wondering if they can safely dive deeper on a repetitive dive. Back in 1999 the Smithsonian Institution in Washington D.C. held a symposium on reverse profiles under the guidance of the Smithsonian’s Michael Lang, the American Academy of Underwater Sciences, DAN, DEMA and others.
The intend was to find out if the traditional statements by many training agencies about the increased risk of DCI, when having reverse dive profiles (from one dive to the next) had any evidence behind it.
After listening to 29 scholarly papers, they came to this conclusion.
Historically neither the US Navy nor the commercial sector have prohibited reverse dive profiles.
Reverse dive profiles are being performed in recreational, scientific, commercial and military diving.
The prohibition of reverse dive profiles by recreational training organizations cannot be traced to any definite experience that indicates and increased risk of DCS.
No convincing evidence was presented that reverse dive profiles within the no-decompression limits lead to a measurable increase in the risk of DCS.
We find no reason for the diving community to prohibit reverse dive profiles for no-decompression dives less than 40 msw (130 fsw) and depth differentials less than 12 msw (40fsw). You can read more about the workshop here.
Still though it is considered good diving practice to try to do your deepest dives first, but if you find yourself in a situation where it is more practical to do the deepest dive first – fear not and enjoy your dive, as long as you stay within the 12-meter difference.
Have fun on your next dive and remember to plan your dive and dive your plan.
Author: Torben Gregersen (PADI MI)