Did you know that objects underwater, including their colours, do not appear the same as on the surface or that sound travels faster through water than through air? Have you ever wondered why scuba divers wear exposure suits, e.g. wet suits or dry suits?
The underwater environment offers unique experiences to divers, but at the same time presents them with a number of surprising challenges. Below are just a few examples.
Light & Colours
Objects underwater appear 33% larger and 25% closer than they actually are. So next time you see a big fish or look at your buddy underwater, remember that appearances can be deceiving.
In addition, as we descend deeper, colours start changing and eventually disappear. In clear water, red colour fades away at a depth of approximately 3-4 metres, orange – 9 metres, yellow – 18 metres, green – 27-46 metres, blue – 46 metres, and indigo and violet at 46+ metres.
As we go deeper everything appears to be gray-blue and shadows are less prominent or disappear altogether. This is one of the reasons why scuba divers take torches with them – by aiming the torch at fish, rock formations or corals, they can see their true colours.
Sound travels 4 times faster underwater and over a greater distance than on the surface.
The denser the water, the faster the sound travels. This means that in denser salt water, such as in our seas and oceans, sounds travels a bit faster than in fresh water (fresh water lakes, rivers, etc.).
Our ears are used to the speed of sound on the surface and our brain can easily determine the direction it is coming from. This is not the case underwater. A boat passing hundreds of metres away may sound as if it is right on top of the diver.
Underwater our bodies give away heat 25 times faster than on the surface. Heat loss is a big challenge for any scuba diver. This is the main reason scuba divers wear exposure suits.
Water conducts heat better than air. Water can also evaporate from various objects, including the diver’s skin and protective suit. In addition, heat can be transferred through the movement of fluids, meaning that an ill-fitting wet suit may cause warm water trapped inside the suit to rise, freeing up space for cold water and thus accelerating heat loss.
Finally, all objects radiate heat. The warmer the object, the more heat it will radiate. A scuba diver’s body is usually warmer than the surrounding water and this results in heat loss.