In the last article, we started to introduce the Advanced course and in this article,
we will discuss the “Deep Dive”, one of the primary reasons people choose to take
the Advanced course. As one of the two mandatory dives needed to complete the
course, the Deep Dive is the part that trains divers to dive to 100 feet (30 metres).
Prior to the Advanced course, PADI Open Water divers are only permitted to dive to
a maximum depth of 60 feet (18 metres).
So why would people even need to dive that deep? Well, the most obvious reason
is that there is often a lot to see slightly below the Open Water diver limit of 60
feet. Here at the Toronto Scuba Centre, we run our Advanced course from Brockville,
a small town on the St. Lawrence River. A number of the dives take place in and
around some of the many shipwrecks that litter the River floor. And most of those
dives tend to be somewhere in the region of 60 to 100 feet.
For those not as inclined to continuously dive Canadian waters only, the 60 to 100
foot depth is also often a critical depth in tropical water diving too. Much of the
diving that takes place in tropical waters, particularly around islands, occurs on
island shelves. Picture an island as the peak of a huge underwater mountain. A
short distance from shore, the peak of the mountain (which is now just under the
surface) usually drops off to great depth. This drop-off is commonly in the form of
a “wall” and more often than not, the wall lies somewhere between 60 and 120 or so
feet under the surface. In order to peer over the wall and take in the breath-taking
deep blue of the ocean, or just to take a look at many of the unique coral formations,
wall breaches or marine life that inhabit the edges of the wall, you need to be able to
dive deeper than the Open Water Diver certification permits.
In any event, not every dive need be down to the maximum depth. Aside from being
able to dive to 100 feet, the beauty of the Deep Dive is that you learn how to safely
dive to a depth that is closer to recreational scuba diving limits. This is where the
skills of really understanding no-decompression recreational dive tables, as well as
safely monitoring our depth, air and ascent rate really come to the fore.
A more critical safety step in learning how to properly dive deep also comes
into play. At 100 feet, there is an increased chance of two major concerns:
decompression sickness and nitrogen narcosis. Paying attention to your depth,
time, ascent rate and knowing the no-decompression limits for the given depth
easily remedies the first concern. Nitrogen narcosis (or being “narced”) is as easily
remedied by simply ascending a few feet, but the critical skill here is recognizing the
symptoms of being narced and acting appropriately.
Finally, diving deep lets you also experience some very cool effects, such as colour
changes, pressure effects on softer objects (you may have heard of eggs or tomatoes
being used to demonstrate pressure changes) and breathing rates. In tropical waters, it
can also be a common depth for some of the bigger sharks…..see how I left that until the end?