Buoyancy and Trim

INTRODUCTION

It has been said that the human body and the subconscious mind remember the prenatal sensation of floating weightlessly in the womb. It has also been said that this may be one of the unconscious motivations for a person to want to become a diver.
Technically, floating weightlessly in the womb is the same as achieving neutral buoyancy: the first time we were suspended, hovering in a fluid without having to swim or move. It is a memorable and desired natural sensation.
Essentially, neutral buoyancy is being just heavy enough not to float up and just light enough that we don’t sink. Much like an astronaut floating weightlessly in space, properly balanced divers hover neutrally in the water. In fact, this is one of the main reasons that astronauts in training practice in large swimming pools.
There are three states of buoyancy in the water. When the diver floats on, or moves toward the surface without propulsion, they are positively buoyant. When a diver sinks, they are negatively buoyant, and when a diver hovers under water, neither sinking nor floating, they have achieved neutral buoyancy.
While it seems simple in theory, neutral buoyancy can be very difficult to achieve in practice for a new diver.
Quite often, new divers will struggle with their equipment while trying to establish neutral buoyancy, kicking and finning relentlessly in an effort not to sink, all the while inflating and deflating their BCD. This usually results in running low on gas early in the dive, and even exhaustion.
However, neutral buoyancy and proper in-water trim greatly reduces diver stress and increases comfort and enjoyment. Proper trim means that the diver presents the least amount of resistance to the water, and uses less energy to move forward; therefore, the diver will consume less gas. When the diver is neutral in the water, they are typically relaxed and calm, which also reduces the amount of gas consumed.
There are many negative consequences directly related to improper buoyancy, which primarily affects the diver and the environment. A diver that is too light, risks unintended ascents and may be struck by surface debris or boats, resulting in a potentially severe injury, while a sudden unintended ascent may cause a decompression injury.
A diver that is too heavy inevitably collides with the objects beneath him, potentially crushing sea life or destroying its habitat.
Overly negative divers also tend to be clumsy, waiving their hands and arms in an attempt to create lift, and inadvertently kicking objects beneath them.
Divers who learned the exercises during their certification course kneeling on the bottom, in the pool and in the open water, will require more time to fully understand the concept of “buoyancy management.” In the absence of SNSI Training, these divers typically will require to perform between 30 and 50 dives after their basic training in order to correct their buoyancy skills.
Thus, instead of focusing on the surrounding beauty, the diver is spending most of their dive time adjusting their equipment and honing basic skills.
SNSI Open Water Divers who have learned to dive using the SNSI Buoyancy Bar System already understand and embrace the concept of buoyancy control. Consequently, they will easily master buoyancy with little practice and experience.
The primary goals of this section are to present the relevant skills and information regarding buoyancy control. Exercises designed to help perfect trim and buoyancy techniques are also described.