By: John Boyer, Diving Unlimited International
In the drysuit business just as in scuba diving in general we are
constantly plagued by false impressions and stories that have been
handed down from one person to another, most of which have been
embellished upon by the storytellers whose only error is the desire to
make a story more interesting.
This article will attempt to address the most common myths regarding
diving in drysuits and allow you, the potential purchaser, to make your
decision with more correct information than the "hearsay" attitudes
that plague most things in which there are few experts.
For the most part this is an incorrect statement. The drysuit itself, with
the exception of the "foam neoprene" suits whose thermal protection is
quickly lost due to compression during descent, provide little or no
thermal protection. The purpose of the drysuit is simply to keep the
diver dry. The garment we wear under the suit, commonly referred to
as "divewear insulation," is what is responsible for keeping the diver
warm. The warmth accomplished as a result of wearing divewear
insulation is a function of the ability of the material to trap and hold air
between the fibers. No garment, including a heavy ski parka, has the
ability to insulate as a result of the material. Its ability to insulate is in
its relative ability to trap air between the fibers. Some fibers are much
more efficient at trapping air than others. Some fibers, such as Type
"B" Thinsulate™ Insulation (100% polypropylene micro fiber*) have
the ability to resist absorption of water and, therefore, are more
efficient as a divewear insulation fabric. The ability to change the
configuration of the divewear insulation on each dive, taking the water
temperature, the diver’s personal metabolism, and the anticipated
activity (more activity generally requires less insulation) of the dive is
one of the most basic advantages of diving in a drysuit. In a 7mm
wetsuit the diver has 7mm of neoprene on each dive, regardless of the
conditions. On most occasions 7mm is either too much or too little.
Also, foam neoprene provides more insulation in shallow water and
less in deeper water.
This is probably the most common fear expressed by non-drysuit
divers. Nearly every diver who has expressed this fear claims to have
had or has seen someone have this problem. When questioned in more
detail about the actual sequence of events, most of these stories are
actually in the "a friend had it happen to them" or "I heard it from a
diver I know" category. On only one or two occasions have I actually
talked to someone who claims they have had this happen to them. On
those rare occasions the person frankly admitted they were at fault
since they improperly operated the equipment or didn’t take the time
to be trained in the proper procedures.
First, if properly operated, the amount of air required to obtain the
"loft" of the undergarment (loft is the term used to describe the
process of making air available so that the fabric can "trap the air"
between the fibers) is very minimal.
Proper weighting in a drysuit is achieved by the diver entering water
too deep to stand up in, holding a normal breath, with no air in the
BCD and minimal residual air in the drysuit. Remaining motionless, the
diver would float at eyebrow level. A diver weighted in this manner
would float at about mouth level if a lung full of air was taken in and
would slowly descend if the "normal" breath were exhaled. This is
neutral buoyancy (In a normal recreational equipment configuration an
additional five pounds of weight should be added to compensate for
the air that will be cast off during the dive. If an 80 cu. ft. aluminum
tank were totally drained the weight difference would actually be
closer to six pounds.) If the diver simply adds air to the drysuit during
descent in the amount necessary to maintain a constant volume, the
ancillary benefit is the maintenance of neutrality with just the air
added to the suit. When dealing with a large volume, double tanks or
other heavy equipment a different technique is required.
The size of the bubble of air necessary to achieve the state described
in the paragraph above would, if the diver were to raise their right arm
toward the surface in a head up position, begin at the wrist seal and
continue down the raised arm about four to nine inches toward the
elbow. The "roving" bubble is always found at the high point in the
suit. This bubble needs to be kept to a minimum. The phrase "a pint
(of air) is a pound (of buoyancy) the world around" means that every
extra pint of air in the suit requires a pound on the weight system.
Excess air in the suit does not increase the insulation value of the
divewear. Proper weighting is important to keep the bubble small.
The bubble described above could not, under most circumstances,
cause the diver any concern. Also, since the diver is neutrally buoyant
it doesn’t matter what attitude (head up, butt up, feet up or belly up)
they are in. Neutrality is neutrality and nothing during the dive
changes the laws of physics and allows the attitude to change the
buoyancy of the diver. Only in extremely shallow water (15 feet or
less) would there be a significant change of volume due to a diver
changing from horizontal to vertical.
A properly trained diver is taught to respond to an "over inflation"
emergency in the very unlikely event it should happen. First, most
modern drysuits are equipped with adjustable dump valves that will
expel air as quickly as the inflator will put air into the suit when the
exhaust valve is positioned at the highest point in the suit. Second, it
is a simple procedure to disconnect the power inflator should it get
stuck in the open position (Simpler in most brands than disconnecting
a BCD power inflator. The DUI hose has a large flange that makes it
easy to grasp, even with gloves, and disconnect.) Third, and by no
means less important, is the fact that a diver trained properly in a
drysuit is taught to recover from a (falsely induced) feet up, positively
buoyant situation. Recovery is accomplished within a minimum of
vertical movement.
One suit manufacturer has installed exhaust valves in the ankles of the
suit to combat this "mythical" problem. All this does is perpetuate and
give credence to a problem that really doesn’t exist. Additionally, the
diver with these valves loses the air in the suit (which, as an ancillary
benefit, provides neutral buoyancy) each time their feet get above the
level position. This requires constant replacement of the air in the suit
to maintain constant volume, avoid squeeze and achieve neutral
buoyancy. The important point is that by installing these valves, that
manufacturer lends credence (by putting equipment on the suit
designed to combat the problem) to the myth of an uncontrolled feet
first ascent. Also worthy of note is that the valve is positioned high
enough on the ankle that a large bubble would still form in the boots.
This is probably the easiest myth to dispel. All a diver has to do is try
on a drysuit and the myth is dispelled.
At the entry level, if a student is allowed to don a modern drysuit
immediately after struggling in and out of a typical wetsuit, the dive
student will probably ask to be allowed to take their course in the
Almost everyone who has taken his or her entry-level course in a
wetsuit can remember the difficulty in donning and removing the
wetsuit. At consumer shows, when putting people in drysuits, the most
common expression heard is "I didn’t know it would be so easy and
comfortable to get in and out of this thing."
In some special cases this statement may be true. As a rule, however,
foam neoprene is not the best choice.
Many pieces of diving equipment are designed to fulfill the same
objective. In each case, the determining factors are the pros and cons
of each when applied to a specific situation.
The major advantage of foam neoprene seals is that they are
somewhat more durable in regard to abrasion.
The negative aspects of foam neoprene seals, in all applications, make
them the poorer choice overall. Foam neoprene is much more difficult
to don and remove due to the thickness of the rubber and the fact that
foam neoprene has a nylon covering on at least one surface.
Foam neoprene is purported to be warmer than latex. This is only
slightly true. If the diver does not descend then the inherent insulation
in foam neoprene is a factor. Since divers do descend, the
compression of foam neoprene negates the insulation. Only because
the material, even when compressed at depth, is thicker is there any
insulation value.
Since foam neoprene compresses at depth, the seal that is water tight
on the surface may leak when compressed. The continuous
compression and expansion (descending and ascending) of foam
neoprene are the primary reasons foam neoprene drysuits or wetsuits
do not last as long as Trilaminate or Crushed Neoprene. The same is
true with foam neoprene seals.
Foam neoprene has a memory. This fact is evident even in the
instructions furnished with the seals. If the foam neoprene seal is too
tight we suggest the customers "stretch" the seal (neck) over a scuba
cylinder overnight. This actually destroys some of the closed cells thus
permanently rendering the seal larger. If left to compression and
expansion the same thing would happen naturally.
High quality latex has very little memory. It will, after stretching, go
back to the original shape more readily. Since latex is considerably
thinner it is more comfortable simply from a standpoint of bulkiness. If
properly maintained, latex will last longer than foam neoprene that is
dived frequently. Proper maintenance includes proper trimming, (so
there are no "saw tooth" edges that lead to tearing) rinsing, dusting
with unscented talcum powder when storing for long periods and
storing in "low ozone" areas.
Since latex seals are made in a cone shape, they are "trimmable" to fit
the individual. Care must be exercised to not trim too much off at one
time. The seals have "guide lines" to help in the trimming process.
Only one line should be removed at a time and the seal should be tried
on after each line is trimmed. If unfamiliar with trimming techniques
consult your DUI dealer or call DUI.
The initial up-front cost of the modern drysuit is somewhat more that
the typical wetsuit. Just as in any investment the price of the item is
only one part of the equation. Modern drysuits, with the exception of
foam neoprene suits, will last so much longer that the effective cost of
the suit is much less. Just as with any item that depreciates, the cost
should be divided by the number of uses the item returns. Dividing the
cost of the drysuit by the number of dives a diver will get from the suit
will yield a "cost per dive" figure. In most all cases the "cost per dive"
will be considerably lower in a modern drysuit than a wetsuit (except
for foam neoprene).
Even with the above information the fact remains that the customer
has to take a relatively large sum of money out of their pocket and put
it on the counter. Most dealers selling drysuits have innovative plans
available that allow the diver to get into a drysuit without causing a
financial burden.
Economics and "just the facts" don’t take into consideration the
increased degree of comfort achieved by the drysuit diver. Imagine all
of the different things in our lives that we could actually do without
but, because we want to be more comfortable, we decide to obtain the
item or convenience. Diving, for most people, is an exhilarating
experience and if those in wetsuits realized how much more enjoyable
their dives would be if they were warm and comfortable most would
invest in a drysuit immediately.
Another thing that many people don’t realize is that if a diver is warm
they are much more efficient. Even those who claim they don’t get
cold suffer a decrease of efficiency by losing body temperature to the
environment. In almost every dive accident recorded, cold can be
identified as a factor. The first thing a diver loses as a result of a drop
in body temperature, is mental acuity. The recognition of a potential
problem can go unnoticed because being cold slows the mental
process. The second symptom of temperature drop is the loss of
physical dexterity. The ability to take proper action to avert the results
of a problem is lost. Many divers lose dexterity without even knowing
they are being adversely affected by a loss of temperature.
People who express this opinion need only analyze the statement. Of
course, those who know most about diving and who are doing it most
frequently will gravitate to the most efficient and most comfortable
way to achieve the desired results. If I wanted to improve my methods
I would first look to see how those who do it best are doing it. The
best reason for professionals or advanced divers to dive in drysuits is
that they know most about it and do it more frequently. An
endorsement of this type by a professional should be viewed as an
unquestionable testimony.
Simply stated, the fact that professionals and advanced divers use
drysuits is the best reason for all divers to use drysuits.
In the past people were warned, "never wear hip boots in a boat or
around deep water. If you fall in the boots will fill with water and drag
you down." To dispel this myth in training lifeguards one of the
exercises used is to have trainees don hip waders and swim lengths of
the pool. Although the boots make it more difficult to swim gracefully
there is no need for additional effort to remain afloat.
If an object displaces an amount of water weighing more than the
object, the item will float. If the item immersed in water is water the
displacement is exactly equal and the result is neither positive nor
negative buoyancy.
Recreational divers should always wear a Buoyancy Compensation
Device (BCD). Regardless of the method employed to maintain
temperature equilibrium the BCD would be used for surface support
and in the event of any emergency.
In the past this statement was more credible than it is today. First,
there is no such thing as "semi-dry." Just as there is no such thing as
"semi-pregnant", a person is either dry or they are wet.
Modern drysuits are made to totally exclude water. If the system is
properly operated it will keep the diver dry. If the suit is poorly
maintained, ill fitted, improperly donned or incorrectly used there is a
chance that the user will get wet. In almost every case where the diver
in a drysuit gets wet one of the aforementioned items is at fault.
Proper training, including donning, diving techniques (including
emergency procedures), removing, care and storing, are all part of the
complete package that makes up the responsibilities when purchasing
a drysuit system. It is the responsibility of the person selling the
product to ensure that the purchaser is either qualified to use the
equipment properly or will get instruction in its proper use. It is the
responsibility of the purchaser or user of the drysuit to ensure that
they are properly trained to use the product safely and correctly.
The additional drag caused by the modern drysuit is nearly
undetectable. The drag caused by the scuba equipment itself far
outweighs any drag caused by the suit that the typical diver would be
hard-pressed to detect any change. This is not to say that an expert
who is accustomed to swimming in a current would not be able to
detect a difference. More important than the drag in some drysuits, is
the fact that the diver’s "range of motion" is adversely effected.
When selecting a drysuit the purchaser should be asked to perform a
series of exercises designed to assess the ability to perform some
simple motions:
raise the leg so that the foot is level with the knee of the other
perform a "figure four" (such as the figure four used to don fins)
reach the back of the neck with both hands
touch hands together stretched overhead
in a kneeling position, sit back towards the feet
The above "range of motion" exercises should be performed with the
divewear and again with the divewear insulation and the drysuit
together. None of the equipment should impede the diver’s ability to
do the "range of motion" exercises. A high-quality drysuit will allow the
diver to do all of these exercises unencumbered.
One of the greatest advantages to a drysuit is that on each dive the
diver is allowed to take into consideration: 1) temperature of the water
2) the diver’s metabolic rate at the time of the dive and 3) the rate of
exercise performed on this dive. As these items vary, so does the
diver’s ability to vary the divewear insulation under the drysuit.
Generally with a wetsuit the diver is either too warm or too cold.
As far as weight is concerned, the drysuit diver is able to adjust the
amount of weight in accordance with their thermal needs. The more
thermal protection they use the more weight is necessary.
It is impossible to generalize weight requirements. For example, one
diver wears twenty pounds of weight with a 6.5 mm wetsuit. In a
drysuit, comfortably equipped for temperatures between 50 and 70
degrees F, this diver will use twenty-two pounds of weight. If a vest is
added (giving an additional 5 degrees of warmth) this diver will wear
twenty-six pounds. Due to the wide variation of body composition
there is no general rule of thumb. Each diver must weight themselves
according to their needs. However, to say that a diver needs much
more weight with a drysuit is incorrect.
In the entry-level course the students are taught that water conducts
heat 25 times faster than air. This means that if a body is immersed in
water colder than body temperature heat is being drawn away from
the body 25 times faster than if the body were surrounded by air. In
cold climates windows are installed with "twin panes" since it is
generally accepted that a dead air space insulates most efficiently.
Household insulation, cold weather sleeping bags and numerous other
heat retention items base their insulatory value on their ability to trap
It simply makes better sense to select the most efficient method to
retain heat in any endeavor. Based on this logic it is easy to conclude:
if there is a need for thermal protection while diving, a drysuit, since
air is the insulator, is always a better choice than a wetsuit.
One of the best attributes of a high quality, well fitted wetsuit is that it
excludes water from most of the body and prevents the "flushing" of
water in areas where water is not excluded. This is more evidence
indicating that if the diver totally excludes water from the system it
would be more efficient.
Since the divewear the diver wears under the drysuit provides the
thermal protection and the amount of protection is variable according
to the three things mentioned earlier, the chances of a drysuit diver
being uncomfortable are minimized. This is true for all temperatures of
water from ice diving to, in some cases, eighty-degree water.
Early on all scuba diving was thought to be too complicated for
recreational divers. In all facets of scuba diving the proper procedures
must be followed. Drysuit diving is no different. It is no more or less
complicated than diving with a BCD. When the first BCD was
introduced, many people in the dive education community pointed and
laughed at the new divers showing up in BCD’s. Many thought they
were cumbersome, complicated, bulky and dangerous. To introduce
them to a new diver would be task loading and asking for trouble.
Today the training organizations all require the use of a BCD in dive
training. Entry level students trained in drysuits tend to accomplish
buoyancy skills with much less trouble and much more accuracy.
Divers trained in drysuits tend to dive more often, take more courses,
purchase more equipment and are less likely to become an
"occasional" or "dropout" diver.
*Thinsulate™ is a trademark of 3M