Today is the second installment on our blog series on DAN’s (Divers Alert Network) 2016 annual diving report. (For more information, see our March 30 post, DAN Publishes Annual Report.) Within the report was a “Ten Most Wanted Improvements in Scuba” list that, among other things, asked for more improvements in how divers manage their gear. Today we’re taking a closer look at some of these proposed improvements and I’ll share some ideas on how to apply them to your own diving practice. Let’s get started.
#1: Correct Weighting
We’ve all experienced it: a dark shadow casts over you as you turn to see a diver descending upon the reef, doing their best Godzilla impression as they lumber and tromp over precious corals and leave plumes of sand in their wake. Haven’t seen that diver? Well…you just may be that diver.
While undoubtedly annoying, the overweighed diver is more than just a nuisance, they are dangerous. Often—understandably—afraid of being unable to descend, divers overweight themselves not knowing the risks of being overweighted far exceed the inconvenience of being underweighted. These dangers include, but are not limited to: rapid descent, leading to equalization issues and possible barotrauma; inability to maintain surface buoyancy, increasing risk of drowning; excess drag, leading to fatigue; loss of buoyancy at depth, leading to inability to ascend without dropping weight. Analyses of diving accidents, including the latest DAN report, support that diving overweight is associated disproportionately with accidents, near-accidents, and fatalities (see here and here).
Now that we’ve outlined why incorrect weighting is a concern, let’s talk about what you can do to dial it in and become perfectly neutral underwater. We’ll move from general to specific by beginning with a simple review of dive physics and later move to the more complex tasks of estimating weight needs and performing pre-dive weight checks.
- Buoyancy, Archimedes, and you: a refresher
One of the key physics concepts divers care about is Archimedes’ Principle , which states “Any object wholly or partly immersed in a fluid is buoyed up by a by a force equal to the weight of the fluid displaced by the object.” In other words, to float, an object (in this case, YOU) needs to displace an amount of fluid greater than its own weight. Displace an amount less than the weight of the object, the object will sink.
Why is any of this important to diving? Think about the difference between a boat and its anchor: the boat, because of the water it displaces, floats, while the anchor sinks. In diving, a mix of physiological factors, scuba gear, and dive medium help us be boats and anchors some of the time, and neutrally buoyant most of the time. (I’ve posted a reference list of these factors on our Google Drive if you’re interested in learning more.) This can’t be emphasized enough: underwater, we avoid diving in a state of perpetual floating or sinking and instead aim to achieve neutral buoyancy, where a consistent depth is maintained with minimal effort.
While you don’t need to become an expert on physics, good, safe diving stems from a solid understanding of these principles. Periodically reviewing them is definitely a safe practice and an awesome resource to help you do that can be found here.
- Estimating weight needs
If this weight stuff seems a bit complicated, it’s understandable, as the calculus of buoyancy involves a wide array of factors including individual body composition, water salinity, wetsuit thickness, gear trim, and lung volume, just to name a few. (Check out this list of the relationship between certain pieces of gear and buoyancy.) So how do you figure it out? The good news is there are a TON of online dive weight calculators out there. The bad news? They are wildly inconsistent. So far, the most accurate guide I’ve found for salt water is 5% of your body weight for 3mm full suits and 10% for 5mm full suits, plus or minus a few pounds. Really, the only way to find your perfect weight is go with an estimation and then do an in-water weight check, which we will review next.
- Predive weight check and underwater positioning
The typical outline of a surface weight check goes something like this: With their BCD empty, a properly-weighted diver will float while holding in a normal breath. Upon exhaling, they will begin to sink. This is the ideal situation where a diver has perfect weight and sinks down oh-so-gently underwater. The not-so-ideal—and more realistic—situation is that a diver either sinks too fast (overweight) or fails to sink at all (underweight). If this is the case with you, no worries, this is why we do the weight check in the first place. All you have to do is add or subtract a few pounds and try again until it’s right.
You might be wondering about the logistics of adding and subtracting weight to achieve perfect buoyancy. First, make it easy by carrying some smaller weight increments that can be added or subtracted quickly. For example, if you estimate you need 14 pounds, don’t just bring along 2 seven-pound weights because you can’t do anything if they are too heavy or light. Instead, bring a mix of 1, 2, and 3 pound, etc. weights so you can actually adjust as you do your weight checks. Where to put all these weights? Floats are awesome for carrying extra weight, along with things like defog and extra mask straps, and are sold at our shop.
While the aforementioned process works as a guideline, there are still some other things that affect how much weight you need. For example, a good deal of divers that complain of being underweight are staying on the surface not because of too-little weight, but because they are unconsciously kicking their legs on the surface. Any movement in the legs or arms will hinder your descent, so remember to relax. Also, the concept of “perfect” weight doesn’t take into account the fact that as you breathe air from your cylinder, the cylinder becomes lighter and you need to compensate for that change in buoyancy lest you become underweighted at the end of your dive, a time where it’s crucial you maintain a controlled rate of ascent. Start the dive slightly (2-4 lbs) overweighted and you should be good to go.
Once you’ve made it under, think about body position, as it’s another good indicator of proper weighting. A head-up foot-down “crawl” position indicates too much weight; butt-up head-down indicates too little. Instead, aim to be more-or-less horizontal and a few feet above the bottom.
- Track your (dive)weight stats
A lot of divers think their log books are only for recording their depth and time–not so. After experience level, the first thing I want to know about my divers is how much weight they used on their last dive and the thickness of the suit they were wearing. Invariably they don’t know, which is a shame because they often end up using more or less weight than optimal. That’s why I always recommend recording: the amount (in lbs or kilos) of dive weight you used, the thickness of the suit (ask the DM, they’ll know), and your weight at the time of the dive. Take that information with you when you dive and pretty soon you’ll be diving perfectly weighted every time.
#2: Greater Buoyancy Control
In the last section, I talked about how weights help offset our natural positive buoyancy and get us underwater but didn’t talk so much about what it means to achieve a state of diving neutral, which is what is usually meant when you hear the term “buoyancy control.” Why all the fuss about buoyancy control? From a safety perspective, its buoyancy affects your ability to perform important tasks like controlled descents and ascents, surface tasks, and maintain a consistent position in the water column. It’s myriad other benefits include better air consumption, protection of delicate marine organisms, and honor of not being the person to whom everyone gives stink eye after the dive. Keep reading to find out how a mix of theoretical knowledge, training, and the right gear can get you neutral every time.
- Understand your buoyancy needs from top to bottom
One of the most concerning sights is watching a diver on the surface with an empty BCD. Remember that when properly weighted, a diver will sink when exhaling. This is great for getting underwater but can be problematic on the surface before a diver is ready to descend. Unless a diver compensates for the negative buoyancy created by the weights, they will struggle to complete tasks like pre-dive checks or donning fins; must work extra hard to stay on the surface and keep water out of airways; and ultimately risk fatigue, panic, and drowning. This is why it’s imperative you always inflate your BCD when entering the water and keep it inflated until ready to descend.
Failure to add air to the BCD on the surface usually happens for one of two reasons: One, divers just forget. Or, two, they mistakenly believe they are “saving” air that could be used during the dive. This, simply, is not true. If you don’t believe me, think back to your certification course and review the oral inflate skill. At most, you needed a handful of breaths to fill the BCD. This amount of gas isn’t going to substantially drain your cylinder unless you are constantly emptying and refilling the it, which indicates a gear problem. However, if you insist on not using the low-pressure inflator, then going old school and inflating orally is ok too, just as long as you remember to do it. Still concerned about using too much air? Consider dropping some weight. Drag from diving overweighted is one of the top culprits in prematurely sucking through your tank.
Many divers wonder how much air in the BCD is enough to complete surface tasks, which is a fair question. A good rule is the jacket should keep your entire head and neck out of the water. If you are constantly trying to talk past water, it’s not full enough. However, if the BCD is so full its constricting your belly, let a little out.
Underwater, the inflation of the BCD should be thought of as a task of making small micro-adjustments. Because of tank weight and typical dive profiles going from deep to shallow, the biggest additions will usually happen during the beginning of the dive. If you are adding more than three to four pumps of air, consider using less next time. At the end of the dive, never, ever add air to the BCD to ascend, as the air in the jacket will expand and cause an uncontrolled ascent. Instead, deflate the jacket and swim up, maintaining a safe rate of ascent. As soon as you get to the surface, establish buoyancy.
- Get the right training
Buoyancy is a skill that takes practice. One of the easiest and most fun ways to do this is to take a class. Peak Performance Buoyancy is offered as a part of the PADI Advanced Open Water course or as its own stand-alone course. In either offering, you will work with an instructor to achieve perfect weighting and trim and perform exercises and skill drills. In addition to buoyancy skills, having the Advanced Certification is often a prerequisite for certain dive tours and is required if you ever decide to do the Rescue Course.
- Get the right gear
A lot of people, concerned about their buoyancy, think they need to bring weight with them everywhere they dive. The reality is they are better off leaving the weight at home and bringing their own suit. Why? Because dive weight for SCUBA is created, more or less, equal, while gear like your wetsuit is not. Let’s illustrate this with an example: Say I’m planning my upcoming dive trip to the Galapagos and know that on my last dive trip to California I rented 14 pounds and a full 7mm suit. Should I assume the same setup will work in the Galapagos? Probably not. Scuba suits compress over time, meaning the 7mm suit I rented in California might not have the same amount of buoyancy as the suit I’m going to rent in the Galapagos. In fact, if old enough, the 7mm could be closer to a 5 or even 4, which would change my weight needs. That’s why getting my own suit would be better because I could gradually drop weight as the suit gets older. The weights? Reserve them for dives closer to home. Between what you spend on the rental and save on luggage fees, you should break even.
Curious about what makes a good suit? Stop in and talk to one of the staff at KHD, we have a mix of scuba and freediving suits available for rent or purchase.
#3: Fewer Equipment Issues / Improved Maintenance
Last, but not least, preventing equipment issues and observing routine maintenance should be a part of every diver’s knowledge arsenal when it comes to gear. The good news is this is achievable with even very limited knowledge of the mechanics of the gear and usually only takes a few minutes of our time before and after every dive. Read on to learn more about how pre-dive and post-dive cleaning procedures and maintenance schedules will keep your gear in tip-top shape and keep you safe.
- Follow pre-dive procedures & be prepared
Like the Boy Scouts, any good diver should use “be prepared” as their mantra. One way to do this is to identify the “weak links” in your gear and check them frequently. For example, mask joints, buckles on BCDs, and fin straps are all prone to failure after time. Keep extras on hand and you won’t ever have to abort a dive. And of course, always perform pre-dive safety checks.
- Follow servicing schedules
Like your car, SCUBA gear has routine maintenance requirements to keep it functioning in tip-top shape. On average, parts like your BCD, regulator, gauges, and computer should be serviced every year (if you’re curious about the exact number, you can always check with KHD or contact the manufacturer directly). However, there are some higher-end brands that allow greater intervals between service. KHD exclusively carries Atomic regulators because they can go two years between servicing . That means the initial investment of a regulator pays off over time because almost $100 every other year on servicing costs is saved.
Regardless of the maintenance schedule, parts are specialized and require brand-specific tools, so servicing is not usually a DIY endeavor. Many dive operations, like KHD, double as service centers. Stacey Herman, our awesome repair tech, is available for maintenance, repairs, and troubleshooting. Feel free to call her at our shop or stop by for a quote.
- Conduct proper post-dive cleaning procedures
The longevity and reliability of gear is largely contingent on how well you take care of it. After every dive, you should rinse all your gear in fresh water. If you choose to use a cleaning solution, make sure it is specifically formulated for SCUBA gear. We sell BCD conditioner in our shop for this purpose. Also, always ensure the dust cap is secured on the 1st stage of your regulator when rinsing it–failure to do this can result in substantial damage.
For more specifics, check out this article in SCUBA Diving magazine. It’s a great resource on pre-dive inspections and post-dive cleaning you should make a habit of performing every time you dive.
Today I’ve reviewed ways you can use proper weighting, good buoyancy control, and routine equipment maintenance to dive safer. Like everything else in diving, you will make the greatest gains in these areas if you take a three-pronged approach: education, training, and the right gear. As always, feel free to post in the comments if you have any questions or want to add any ideas of your own. Keep an eye out next week for the third, and final, installment of the “ten most wanted” series.