Basics - Theory for Scuba Divers

2. Additional equipment

Now that we've studied the basic things necessary to do a Introductory dive and that every trained diver should know by heart, let's turn to the things and issues that are just as important, but makes the difference between a well trained scuba diver and a diver in training. In addition, we now deepen some statements about the equipment

2.1 The divers knife - a tool, no weapon -

As you can easily see above, there are many different diving knives, in all sizes, shapes and colors. Depending on the design, they can be worn on the leg, fastened to the jacket or even screwed onto the medium-pressure hose. A diving knife is first and foremost a tool that we need to cut ourselves or our partner off a leash, fishing line or fishing net if necessary. The blade should be stable and form a unit together with the handle that does not give way at every stress. For most knives, however, you will not be able to test this requirement because the plastic handle cannot be removed. With the exception of knives made of titanium, all scuba knives are susceptible to rust, so you should always lightly grease your knife with petroleum jelly and check the protective layer from time to time. But even if you do not do that, your diving knife will last a long time. Like all other equipment, the knife has to be rinsed with fresh water after the dive and dried in the shade. Some divers believe that the blade of the knife should not be sharpened to avoid injury. Okay, the idea is not outlandish, but anyone who has actually landed in a fishing net and got tangled up in it, will agree that the blade of the knife cannot be sharp enough. So much confidence must we have in our abilities that we can handle knives with care. In the local kitchen that works very well too. A diving knife is an important part of diving equipment and not a toy. Those who are afraid of knives (xyrophobia, aichmophobia or optionally also machairophobia) can also do very well with suitable scissors or use the cutter shown below. However, both tools have the disadvantage to be useless when cutting thick ropes and who has ever tried to remove a rope from the propeller and the drive shaft, will plead for the knife.

Cutter

Scissors

Scissors and knife combined

2.2 Diver's watch

The diver's watch is more of a statement today than a much used tool underwater. With the diver's watch today one shows rather its affiliation to the group of the divers, than that one uses them really for diving. This is not because the watches are superfluous, but it is the advancement of technology in general, and in particular, the invention of the dive computer. A good dive computer you get today for less than 400.- Euro. And this computer does all the calculation for you. Since you cannot think and combine well, depending on the depth, anyway, the dive computer is a great help for many.

In the past, the diver's watch was an important instrument for determining decompression times, and if the computer ever fails, which is very rare but not impossible, you can safely end a dive today by using the clock and decompression table. In addition, a beautiful diver's watch is also a gem and you know what you could wish for Christmas or your birthday. Only return your diver's watch to authorized specialist workshops for repair and battery replacement. After every service, the water resistance of the watch must be checked and not all watch shops can do that.

If you want to buy a diver's watch, pay attention to the following details:

Buy the watch from a stockist.

The glass should be made of sapphire crystal, as this is particularly scratch-resistant.

The crown should be screwed and O-ring sealed.

The rotary ring may rotate counterclockwise only to prevent accidental twisting of the rotary ring. Otherwise the dive time seems too short and a decompression accident may be possible.

The clock should be tested at least to a depth of 200 meters. Not because you dive so deep but because that is a quality feature for the tightness of the clock.

The bracelet should be long enough to wear the watch over the diving suit.

The figures and the clocks/pointers should be luminescent to guarantee a good readability even at Night dives.

2.3 The depth gauge

The best diver's watch is nothing worth if we don't know how deep we have been. The trio, watch, depth gauge and decompression table has been the tool of choice for decades to make a correct decompression. Generally the depth gauge doesn't measure the depth but the ambient pressure. These measured pressure will be transmit via levers and gears on a shaft to which the pointer is attached. The first depth gauges worked after the system Boyle-Mariotte and were made of a pipe which was open only at one side. These pipe was fixed above a scale, which showed the depth in meter. Depending on the pressure, the water penetrated into the pipe and at the separation surface water / air you could read the depth. Simple and inexpensive, but outdated and inaccurate.

Today's standard depth gauges work with a membrane that absorbs the pressure and passes it via the lever and gearwheels to the pointer.

Today's standard depth gauges

Apart from that, the same criteria apply to the depth gauge as for the diver's watch, because in the end it is also a watch, which however shows the water depth. Another difference is that you have not to replace a battery because it hasn't one. However, since there were resourceful people who have united the clock, the depth gauge and also the decompression table in one device, the depth gauge has become quite obsolete today. If you still want to buy one, pay attention to the following details. The dial should be luminescent (fluorescent), so that it can read well even at night dives, without having to light it up any longer. The decompression levels, 3 to 12 meters, should be highlighted to make it easier to stop at these steps. The glass of the depth gauge should be made of sapphire crystal, as this is particularly scratch-resistant and a height adjustment and zero point adjustment would be nice to have. These two features have only the higher quality depth gauge integrated. They serve to adapt to the different ambient pressures at the sea and on the mountain lake as well as the temperature adjustment. Some depth gauges also have a so-called drag pointer, which stops at the maximum depth of the dive and is therefore a great help when there's a need to a decompression. The bracelet should be long enough to be worn even over a drysuit.

2.4 The divers computer

Again, who would have guessed, many different models, which often have got so many features that one of us is hopelessly overwhelmed. As with every computer. Such a computer is a very practical and recommended tool. These devices can do much more than just show dive time and depth. And if you have informed yourself on the Internet or at a trade fair about their abilities, you finally come to the conclusion that these things often can do much more than you need. But that does not matter, because you are not forced to retrieve all skills and it comes in handy your computer is also your logbook That's not so bad. So you can't forget to log your dives. The Cosmiq from the company deepblu not only offers you a logbook function mobile app on a website, but also combines them with a "facebook" for divers. The fact that some computers also display the pressure of your tank in digital form by means of transmitters at the first stage, is chic, too, although you should rather still have a look on the pressure gauge. Because even a battery in the computer can quit its duty and the law of Murphy has taught us that something usually happens in a not suitable moment. Because a dive computer calculates your own decompression time and depth based on dive time, depth, and dive profile, you cannot pass the computer on to a buddy or your spouse if you no longer want to dive. Of course, the computer does not know that the user has changed now and then your wife may have to decompress for a very long time, even though it's only her first dive. You would then have more time for serious dive stories at the bar but if your wife has decompressed to the end, there could be trouble. So, dive computers cannot be easily lent to other divers. Before buying a dive computer, consult a stockist and inform yourself at like-minded people. Also, keep in mind that your eyes are not as fit as they used to be in youth and there may be problems reading the often small digits and letters. I am 58 and I have problems with the little digits. My colleague used a specially-made magnifying glass for this purpose, but that's not for everyone and perhaps a little bit ridiculous. Care and treatment see watch and depth gauge. Tip: If you have the opportunity to rinse your equipment in rainwater and thus in nearly lime-free water, you should do so. Because next to the sand is the lime from our tap water, a mineral that can adversely affect the function of our equipment.

2.5 The divers flag

Divers "show their flag" and should do so in the water to protect themselves. In the international flag alphabet, there is the "A" flag or "Alpha" better known among divers as Alpha Flag.

In most European countries this flag is set when divers are underwater. It is usually hoisted by the captain and has, according to the international rules, also a minimum size that we diver in everyday life can't comply....