One Star Diver (ISO)
Welcome to the Underwater World5 Tópicos
Diving Equipments6 Tópicos
Our First Contact with Water9 Tópicos
The Effects of Changes in Pressure4 Tópicos
Breathing with Scuba Set10 Tópicos
Limitations of Breathing Air Underwater3 Tópicos
Planing and Monitoring Your Dives6 Tópicos
After the Dive5 Tópicos
About the Practical Skills12 Tópicos
HOW CAN WE ADAPT TO LIGHT CHANGES?
Apart from always having to wear a mask underwater, we must accustom ourselves to the loss of light intensity.
The light of a torchlight can help us recover the colours of what we observe underwater. That happens because the distance between the torch and the object is so short that there is no space for selective absorption.
A torch is also advisable if we plan to explore places where light intensity is minimal, such as caves and small grottoes.
More powerful spotlights can illuminate a larger area but are cumbersome to carry while diving (often a small torch in the BCD’s pocket will suffice).
If you wish to take pictures when in deep or low visibility water, you will need to use a flash for the colours to appear. When checking the photos, it is interesting to observe details that went unnoticed before due to the apparent monochrome bottom.
When we look around on the surface, we can distinguish objects (boats, bathers, the coastal landscape, etc.) up to a distance of hundreds of meters. However, when we are submerged, visibility decreases drastically: only a few meters away from us we may not see objects clearly due to particles suspended in the water. Beyond that, all objects fade into the blue-green backdrop.
In conclusion, the diffuse luminosity that hides objects is due to particles in suspension and the lack of colour is due to selective absorption by the water.
Visibility will be higher or lower depending on the amount of suspended particles. Visibility on a given day will condition the distance we keep from our dive buddy so we don’t lose sight of him/her and also our orientation underwater.
As we cannot take references (from distant objects) in the same way we would do ashore or on the surface, we must be aware of the bottom structure, its slope, depth and other
features which, together with experience and knowledge, al- low the dive leader to return to the anchor or beach.