How do we team dive with the many different types of dive computers and decompression algorithms on the market? It’s not often that we see a team of divers all diving the exact dive computer. In this months blog, I thought it would be a good idea to have a discussion about procedures that should be considered when you are team diving with dissimilar computers.
First off, lets talk about the why this could be an issue. Not all dive computers are created equal. Most dive computers have similar basic functions. They display current depth, NDLs (no decompression limits), they track nitrogen loading, ascent rate, and log the dive. However, different computers use different algorithms/decompression modules and this can give divers different NDLs times than their teammate's computer. This can translate to some confusion while diving if we do not plan appropriately.
Here's why your dive computer may be giving you more or less time than your teammate's computer. Different algorithms/decompression modules calculate dive data differently. While all of these algorithms are theory, most of them have gone through testing by the Navy, NOAA, and other various organizations. This doesn't mean they are flawless, just tested! The most common decompression modules that are in use today are Bulhlmann, VPM, and RGBM. Do a google search and learn about them. Cool stuff! There are also variations and conservatisms to each of these models such as gradient factors, deep stops, etc. Some dive computer manufactures add in there own unique variations to these deco modules such as Pelagic’s DSAT or Z+. There are many possibilities! The chances are that your computer is running a different deco model than your teammates.
Recreational Computer Dive Planning.
So what should computer dive planning look like to a recreational diving team that stays within NDLs (no decompression limits)? I believe that basic computer dive planning should start with a conversation about maximum depth, maximum time, minimum air pressure, and a dive leader. Most dive computers that run any sort of decompression model has planning software within its menus. When planning out a dive with your team, every team member should find their NDLs on their personal dive computer for the maximum depth of the dive. What you may notice is that some of your teammates computers will be more or less conservative than yours. This means that your teammate may be given more or less bottom time for the dive. This is because their computer may be running a different algorithm or it may be set on a different conservatism for the same algorithm. Many dive computers today have user adjustable algorithms to closely match your teammates computer. You can find out if your computer has this capability by simply reading the user manual. Yes, you should always read your computers user manual. If the team cannot match NDLs, you should simply dive to the more conservative computer. If the diver ignores the NDLs of his computer because the other team member is getting more bottom time out of his, you will bend your computer causing it to enter into emergency decompression mode and locking you out for the next 24 or so hours. Dive within the limits of the more conservative computer.
Technical Computer Dive Planning.
How should computer dive planning work for Technical Divers? First off let me say that I am a proponent of cutting dive tables for every technical dive and keeping them in a pocket or something easily accessible. Even when diving multiple computers. Cutting tables can make you more intimate with the dive plan and provides an extra margin of safety. It’s too easy with all the software available such as ultimate deco, v-planner, and the planning software available in most dive computers today to have this information. Your smart phone is capable of this as well. I understand that computers give more realistic dive data than planning from a square profile. However, they are still electronic devices being used underwater to lead you through a decompression schedule attempting to keep you from getting bent.
That being said, I conducted an online research of how different diving teams plan their dives when the team is using dissimilar dive computers and dissimilar algorithms. As expected, I received many different opinions. Some diver teams said they plan their own dive based on their personal preferences of algorithms and conservatisms and some use identical plans.
Here are two examples below:
A tech diving team made up of two divers uses their own software and preferences to plan out their individual decompression schedule. Diver 1 uses Bulhmann ZHL-16 with a GF (gradient factor) of 30/70. Diver 2 also uses the same Bulhmann ZHL-16. However, he chooses to use a GF of 50/80. Their deco schedules look totally different. They dive and stay together for the same depth and bottom time. However, when it is time to leave they go at decompression alone diving their independent deco schedules. Diver 1 is making deeper stops along the way up while diver 2 is stopping shallower and surfacing much sooner than diver 1.
You cannot call this type of diving team diving. If something was to go wrong they are unable to assist one another because they are solo diving. Loss of deco gas, toxicity issues, and every other situation that may appear must be handled alone. However, in overhead diving environments, sometimes scattering the team at different places may be beneficial. This is not due to the fact of opposing views on decompression theory. It is due to restriction and over-crowding issues in a small space. Doing that requires a lot of training and pre-planing to make sure that the divers are able to assist each other if the need arises.
A tech diving team made up of two divers begins to plan out their dive. Diver 1 is diving a computer that uses VPM while Diver 2 is diving a computer that uses Bulhmann with GF. They run a few deco schedules on their planner and agree on the schedule that Diver 1’s VPM computer puts out. Diver 2 adjusts his GFs to closely match the agreed upon deco schedule. Diver 2’s computer has only a small variance from the agreed upon schedule by a 10ft deeper stop for 1 minute. The divers agree to stay together while diver 2’s computer requires the extra stop. They stay together through the entire dive working as a team and aiding one another when needed.
I believe that this is the best way to plan dives when diving in a team with dissimilar dive computers using dissimilar algorithms. During my online studies and conversations on this subject, most divers use the planning method from example 2.
Dive safe and within your limits!
I get this question often. My answer is always the same. If you are going to be a diver, yes! Owning your equipment plays a big part to you comfort and safety underwater. It makes your more confident and safe while diving. There are many benefits to owning your own equipment. Lets look at some ways that owning your equipment makes your a better and safer diver. Also, I've included some tips for your consideration when you decide to make your gear purchase.
Familiarity Builds Confidence:
Diving with the same piece of equipment every time that you dive will build confidence in yourself and in your gear. You can customize your gear and add accessories that stay put. When you rent different gear every time you dive, you will have to relearn where everything is. Being familiar with your equipment will drastically cut down response time to issues. For instance, knowing where your line cutter is during an entanglement issue will make the situation go much smoother rather than having to search for it. After purchasing your new equipment and getting your accessories placed, you should go to a pool or a familiar dive site and work on developing muscle memory and practicing skills with it. This builds confidence. I will put my BCD on in my house and practice taking on and off the line cutter, lights, reels, and etc. This makes me more efficient and confident when i’m diving. Never believe that without practicing these skills that you will be able to perform well when its needed. I’ve heard it said, “the worst you perform during training will be the best you perform during an emergency”. Practice makes proficient.
What should I buy?
Most divers already own their personal gear (mask, fins, snorkel, wetsuit, and boots). The life support system is considered: the regulator system, the BCD, cylinder, and the dive computer. In my opinion, you need to own the following at minimum; dive computer, regulator system, and BCD. There are generally 2 ways to buy your equipment. Piece by piece or a complete package. You will save a good deal of money when you buy a complete system. Many manufactures offer discounts that save several hundred dollars when you buy a gear package. Check out these packages below.
However, if you decided to buy your gear piece by piece I would suggest that your purchase a dive computer first. Not all dive shops rent dive computers and this is especially true if your going on a trip out of the country. Owning and learning your dive computer is one big part of your diving safety. The dive computer at minimum monitors your ascent rate, your no decompression limits, your depth, surface interval, and most even log the dive profile. There are many makes and models with tons of bells and whistles. Most entry level dive computers can be bought for around $250-$300. Chose one that meets your diving needs and don’t buy twice.
New or used?
Buying used gear sometimes can cost you more money than buying brand new gear. The first thing you must do when buying used equipment is to have it serviced by an authorized gear technician for that particular brand. Gear must be serviced yearly. Don’t chance it and kill yourself trying to save money. Die of something awesome instead. You cannot survive underwater without properly working equipment. There are parts that move every time you breathe and they take wear every time you breathe. It will wear out. If you cannot afford to have it serviced, you cannot afford to own equipment. Rent instead. Simple. Rant over. If someone local cannot do the service, the gear will have to be sent off. That generally takes at least 2 weeks. Most shops charges $35-$50 per stage (A reg set has one 1st stage and two 2nd stages) plus the rebuild parts. That can cost you around $200-$250 per year. Buy the time you pay for the used gear and have it serviced, you may have more invested than if you bought new gear. You need to take that into consideration when purchasing.
If you have any questions about purchasing gear please feel free to contact us! We will be happy to answer any questions that you may have. Thanks!
Working with divers almost on a daily basis, I’ve observed some bad diving habits that I want to point out. Most of these things are slips of the mind or just plan carelessness that causes trouble later in the dive. Check out below some of these bad habits.
Not checking air pressure before getting into the water.
Don’t skip this step. Before ever putting your equipment on your body, you need to know if the cylinder has sufficient air. I’ve been on many boat charters where divers gear up, jump in the water, and descend only minutes later to find that their tank was near empty. O’rings fail and can leak air out with you hearing it. Sometimes dive operators make mistakes and can skip a tank during filling. It is your responsibitiy to know if you life support equipment will support your life. Check your air and all of your gear.
Not discussing a dive plan.
Many times divers jump in the water without discussing any type of dive plan. At minimum you should discuss with your dive buddy maximum depth, maximum time, minimum air pressure to surface with, and who is leading the dive. You need to know how deep your going, how long are you staying (what’s your NDL?), how much air will you surface with, and are you leading or following? These are just the bare minimum things you need to discuss. This simple conversation can save your life. Don’t dive without a plan. Most all diving deaths and accidents happen when divers are diving beyond their limits. Decompression sickness is real. If you overstay your limits, you will get bent. If you run out of air you can drown. If you don’t stay together you will get separated and spend most of the time searching instead of diving.
Rushing and Overheating
There is no reason to rush to set up your equipment. You are entering into an environment that you cannot live in without the support of correctly operating scuba equipment. Do not dive if your equipment isn’t working correctly. Every year there are multiple diving deaths because divers choose to dive with a known equipment issue. Don’t be that guy. Bring extra equipment and/or know when to call the dive. During the summer a lot of divers overheat. They rush setting up their equipment and skip steps trying to get into the water to cool down. Take a few minutes and jump in the water to cool down if your getting hot. It is better on your body. It helps avoid decompression sickness. It will help you conserve air because your not jumping in already worn out. You are less likely to make mistakes in setting up your equipment when your not overheating. Slow down and you will speed up.
Not hydrating before diving
It is believed that a leading cause of decompression sickness is due to dehydration. Start drinking water a day or so before your dive and stay hydrated. You blood becomes thicker when your dehydrated. Imagine a bubble rising in syrup and then one rising in water. The bubble will rise much slower in syrup. We are taught to ascend slow. We are infact decompressing on every dive we do and trying to eliminate bubbles and bubble formation. Staying well hydrated will aid in this process. Also, don’t drink alcohol before diving. Not only does it impair your judgement, it also dehydrates you. Save that for later.
Having bad buoyancy control
Buoyancy control is a skill that you will continue to develop the more you dive. However, it is a critical skill for safe diving. Just about everywhere I dive, I see divers new and old silting out the bottom with their fins. Divers come to see and experience the dive site, not silt. Don’t be the guy that ruins visibility for everyone else. Your body should be horizontal in the water column and none of your gear should be dangling about. Kicking coral can kill years of growth. Between oil spills, toxic water discharging and bad environmental choices by big cooperations and government, we have plenty of other things already killing it. We definitely do not need divers helping with that. Imagine yourself in a 3rd person view. How is your body positioned? Where are your fins? Bad buoyancy control shows a lack of diving skill. Read last months blog to learn how to weight properly and/or take an advanced buoyancy course with me.
These are many more bad habits that divers tend to hold on to. Think through your diving habits. Are they safe? Make changes to become the best and safest diver that you can be.
What do you look like underwater? Some divers walk across the bottom, some use their hands and fins to swim, and some kick like they are riding a bicycle(don’t do any of that). I have heard some instructors tell students that a divers underwater orientation does not matter as long as you are breathing. However, I want to share with you today a few things that will help you become more stable underwater and look great while doing it.
Check out these pictures below. Which diver looks like they are more streamlined, stable, and will have the least amount of resistance while moving underwater.
If you chose the horizontal diver, your right. This is called being trimmed out. This divers orientation creates the least amount of drag underwater. On the surface of Earth, we walk upright because it is the most efficient method of travel. However, this is not efficient underwater. When we dive underwater we are in a totally different environment like an astronaut in space. Like astronauts, divers have to practice how to position themselves and move in a foreign environment. Underwater, the most effect way to move is in the horizontal trim position.
Being properly weighted is the first step to getting in trim. Where you place weight on your bcd has a direct effect on how your body will be positioned while diving. Placing all the of the weight toward the divers waist or butt can cause a head up - butt down position. Placing all the weight towards your shoulders can cause a head down - butt up position. Because everyone's body is different, weight positioning will vary to each diver.
The first thing to do is to get the right amount of weight on you. You want to check for proper weighting with a tank at 500psi. This is because your tank loses weight and becomes more positively buoyant as you breathe it down. Checking your weighting with 500psi left in the tank will ensure that your are neutrally buoyant at the end of your dive. Doing this with a full tank on will make you positively buoyant at the end of your dive and you will have difficulties staying down during your safety stop.
Here is how to find the right amount of weight.
With a dive buddy helping, (keep regulator in your mouth during this incase you sink)
1. Take your tank down to 500psi
2. At the surface, deflate your BCD and hold a normal breath of air in your lungs.
3. If you are weighted properly, you will float at or near eye level. If you release the air from you lungs you should begin to sink.
4. If you are overweighted, your will sink. Remove some weight and repeat step 2.
5. If you are underweighted, you will float above eye level. Add weight and repeat step 2.
If you have been diving over/under weighted, you will immediately feel the difference and the freedom of diving neutrally buoyant. Its easier to control yourself, you will consume less air, you will slip through the water with much less effort, and tons of other benefits will come by diving neutral.
Now, being weighted properly does not necessarily mean that your diving in the horizontal trim position. This has to do with weight placement, practice and discipline. Placing all the of the weight toward the divers waist or butt can cause a head up - butt down position. Placing all the weight towards your shoulders can cause a head down - butt up position. Use your dive buddy to help move weight around to help you achieve the horizontal position. You shouldn’t have to contort your back to achieve this position. You do want to arch your back a bit, but it shouldn't be tiresome or painful. If your having to twist your body to stay horizontal, you need to work on weight placement. Stay still while hovering and see if you lean to one side or the other. If so, make adjustment to weight placement. Take pictures and judge yourself against the pictures above. Keep your legs bent up at a 90 degree angle like in the picture above. Make a conscious effort to not kick up the bottom. Kicking up the bottom is a great way to show other divers your skill level. They will probably not be happy that you trashed the visibility. Another thing to consider is that kicking up the bottom does damage and can kill coral and other delicate marine life.
Keep practicing. Practice makes progress! Also, consider taking an advanced buoyancy course. I can help you get trimmed out and diving like a pro.
I hear this question almost weekly when promoting speciality courses. "Why would I spend money on a course that doesn’t get me deeper or access to more dive sites?” A lot of divers that I have discussed specialty courses with feel like they are just a way for dive shops to make more money off of the student. Well, I do make a living as a full time scuba instructor and selling courses is beneficial to me and my family. So yes, one reason I teach these courses is so I can make money.
However, the primary reason that a diver should consider speciality training is for their personal development as a diver. Much like a fitness trainer can hone the way you work out, specialty courses are designed to help you improve your diving skills. For example, the advanced buoyancy course may not gain you access to deeper depths and you probably won’t ever get asked for that cert card on any dive, but the skill set you gain sets you apart and makes you a better diver.
I recently experienced this working out in the gym. I watched a bunch of youtube videos and read forums on how to work out to save the cost of hiring a personal trainer. The outcome was pretty bad. My form was off and I was not getting any of the results I wanted. I finally hired a trainer. It was amazing. In my first session he immediately pointed out bad habits that I was using and corrected them. I am much better off because of the experience. It was totally worth the money. This is completely applicable to specialty scuba courses. Its easy to pickup bad habits with scuba like overweighting, swimming with your hands, and being vertical in the water column just to name a few. While diving is the best sport ever, it is important to note that diving requires discipline and practice of many perishable skills sets to stay alive and well. It is not like riding a bicycle.
Specialty training with an instructor can help you in your development as a diver. We can point out bad habits and show you alternative ways to improve you. Specialty courses are an investment in yourself. As a scuba instructor, I am always seeking out instructors and mentors to make me better. I love learning and there is no youtube video, blog, or forum that can compare to time spent with a trainer. It could take years to master skills on your own that can be taught to you in just a few dives from a qualified instructor. Plus, I like making friends. I've meet some really amazing people in my career as a diver. In our fast pace culture it’s easy to go through long periods of time without meeting new people. I have seen many amazing friendships come out of diving courses right here at my shop. So during this dive season are you going to take time to invest in yourself? You never know where it may take you!
Check out some of these speciality courses that we offer.
Advanced Buoyancy Control
Advanced Nitrox Diver
Night/Limited Visibility Diver
Search and Recovery
Wreck Diver/ Wreck Penetration
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Diving tips, techniques, and disciplines for safe diving.