Precision Diving

One area of scuba diving education that seems to get little attention is how to pack your gear. My very first scuba diving vacation was when my wife and I got married in Hawaii and did our honeymoon in Tahiti. I toted a full sized, scuba suitcase from Chicago to Maui to Honolulu to Papeete to Bora Bora to Moorea, then back to Honolulu and finally Chicago. Each leg of the journey, I had to pay extra for the weight (and extra bag) of scuba gear. I carried way too much unneeded stuff. In today’s economy, the airlines are looking for any reason to bend you over and nail you in the keester with luggage fees. So planning how you pack, can save you some money in the future. (more…)

“We don’t make any money on our open water classes. We hope that the open water students will buy equipment from us once they are certified.” I first heard this type of statement was during my PADI IDC when we were discussing course pricing. As a business person, this didn’t make much sense to me, but I could understand the rationale that a business uses a product or service to drive sales of other products or services. That was six years ago. I’ve had plenty of time to think about this and the more I ponder it, the more I have realized that this mentality is slowly killing the scuba diving industry. (more…)

I get asked many times about what kind of doubles people should get when they want to move into technical diving. Should they get 130s, 100s, 120s, or aluminum 80s? There is no one right answer for selecting which size tanks. However, special consideration must be made in regards to selecting the manifold, valves, and bands to build that set of doubles. (more…)

Ever hear the saying “There’s more than one way to skin a cat.”? Basically what it is saying is that there are multiple ways of doing the same thing. In scuba diving, there is a multitude of methods, procedures, etc for diving. But what is the best one? This article will look at a few areas of recreational scuba diving and describe what are the best practices for those areas and why.

Propulsion
Do you remember when you did your initial open water course? Did the course materials or instructor discuss propulsion techniques? Most likely not. Most open water courses do not teach propulsion techniques as they assume the students are swimmers. When swimming on the surface, most people use a kick called the flutter kick. Most open water classes will just have you flutter kick around the pool or open water as that is what you probably learned when you were a kid in swimming lessons.

The flutter kick is the most inefficient propulsion technique in scuba diving. The traditional flutter kick uses the largest muscles in the body, the thighs. When you exercise, your muscles metabolize oxygen and the by-product of this is carbon dioxide (CO2). CO2 is a killer in scuba diving. It is more narcotic than nitrogen and can lead to a diver blacking out. So when you are swimming with the flutter kick and working underwater, you are building up CO2 in your body. Secondly, the flutter kick directs water down. If you are diving in sensitive areas such as a reef or shipwreck, you run the risk of damaging that environment or silting it out. A silt out can also be a killer in scuba diving.

The best practice for propulsion techniques is the frog kick. The frog kick directs water straight back from the diver. It does not direct water downward, instead it directs water directly behind the diver. Thus significantly reducing the risk of damaging sensitive aquatic environments and silting out confined areas such as shipwrecks. The frog kick also does not use the thigh muscles as much as the flutter kick. By using more of the glutes, hamstrings, and a little thigh, we can reduce how much CO2 we are building up in our bodies.

Equipment
Currently, the trend in scuba equipment is that people use a jacket style buoyancy control device (BCD). These BCDs fit people like a vest. They have a variety of features. Many include weight integrated, built in tank bands, and pockets. They also use plastic buckles and velcro to secure around the diver’s body. One big problem with jacket style BCDs is that they are very bulky. The weight pouches on these types of BCDs are normally right around the “love handle” area of the body. This now moves the weight off our back and possible off our center of gravity.

The best practice for a BCD is the backplate system with a one piece, continuous harness. This configuration is very streamlined and not bulky. Backplates are made of either stainless steel (SS) or aluminum (AL). The SS backplate is 6 pounds negative, that means you can take six pounds off your weight belt. The AL backplate is 2 pounds negative. Many divers have found that carrying weights in pockets or on a weight belt is not comfortable. The backplate puts the weight on the divers back where it can be supported easier than hanging off the hips. The one piece continuous harness, not only is streamlined, but it also eliminates many failure points. By getting rid of plastic buckles and velcro, the one piece harness will be much secure. If a diver also out grows the harness or needs to replace it, the webbing only costs about $15 and can be purchased at any hobby store. Jacket style BCDs, when out grown, must be replaced and can be very expensive. The backplate system can also be paired up with a wide range of wings (i.e. the air cell or BCD). If a diver is going to move between a single tank rig and double tanks, the backplate doesn’t need to change. You just swap out the wing for which type of rig you want to dive.

There are many other best practices when it comes to equipment. To many to list out here. But you should get my point. We are looking for equipment that enhances our skills, not replacing them. Equipment should also restrict potential failure points, either real or perceived.

Trim
First, let’s look at trim. Trim is the position a diver is in. In order to move horizontally, with little resistance, through the water, we must present the smallest footprint as possible. Just like with cars being aerodynamic, we must be just as aerodynamic. The most ideal position is to be completely horizontal in the water. This gives us a small footprint and reduces drag as we move. Now, when we move up in the water column, you were probably shown to be in a vertical position, rotating around, looking up so you don’t run into the bottom of the boat. Well, remember when I mentioned that when we present a small footprint, we move very efficient through the water. When ascending, we want to ascend at a very slow pace. If we are streamlined going up, it just makes it easier to ascent faster than what we want. In order to ascend in a controlled manner, we must present as much drag as possible going up. This means we must remain in a horizontal position when ascending. This creates a large surface area to increase drag. Thus allowing us to control our ascent. The best practice for measuring trim, is that a diver should be no more than 30 degrees of horizontal. For technical divers, that measurement is 20 degrees or less.

Moving Forward
As you can see, I just touched on a couple areas where we can apply best practices. There are many other areas and I will write about those in future articles. So when you are taking your next class and are told/shown multiple ways of doing them, ask which one is the best and why.

If you found this article helpful, please leave a comment or submit a Digg for it. As always, I welcome your questions and comments.

Dive Safe,
Duane Johnson
Precision Diving