Mares Horizon

Mares Horizon: a revolutionary way to go underwater. My feelings after the Try Horizon, my test with the Horizon on my shoulders. Perfect simplicity, noise relief. Immersed in silence I was just an observer.

May 2022, Isola delle Femmine (Pa)

The long awaited moment of the “TRY HORIZON” has finally arrived for me and my dearest buddies Silvia, Rosalba, Francesca, Mariateresa and Martina, at Diving Center Saracen together with our instructor Tony.

We are ready to try the  Mares Horizon SCR and we expect more than one test. To be able to live a wonderful experience, capable of upsetting our way of diving!

An exhaustive theoretical lesson

The test began with a very interesting and comprehensive theoretical lesson. Tony described to us with great skill (and a lot of patience …!) the different components of the Mares Horizon and clearly explains the function of each of them.

After more than two hours of very fruitful chats, we have a more global vision of this equipment and its great potential.

My first reflections

In fact, since I started to get interested in the semi-closed HORIZON circuit a few months ago, I was immediately attracted by its versatility, as it is very intuitive and suitable for any type of diver, recreational or technical.

In my opinion, the MARES HORIZON is first and foremost suitable for us, women: 12 kg against the 40 kg of a bi-cylinder… that’s no small feat!

A non-negligible difference for the back of even the most trained divers!

In fact, being very light and compact, it can be taken anywhere without much effort.

Horizon in my opinion

Before moving towards the heart of today’s topic, I would like to specify that I will leave out too technical aspects in relation to the design and operation of the HORIZON (while not remaining superficial …!) In order to focus on this exciting experience I lived in our beautiful natural gym of Isola delle Femmine, a few steps away from the Diving Center Saracen with shoes, focusing on our feelings of “bubble-free” divers!

Promising simplicity, so that the user can concentrate on something else, the Mares Horizon rebreather looks like a rigid “backpack” to which one or two Nitrox cylinders are added in sidemount mode, on the sides.

Mares Horizon

Attractive and well finished, the first thing that surprises, and that differentiates it from other rebreathers, is certainly its weight!

Those who are used to CCR rebreathers or have already approached them know that they are a rather heavy equipment and not necessarily easy to handle, that is, they require considerable technical and theoretical preparation.

Here it is quite the opposite! In the sense that all the drawbacks of the RAC seem to disappear!

Horizon consists of…

The HORIZON consists of a harness and a unit that contains all the electronics, the O² sensors and two canisters. In which a so-called fixing material is inserted. ” scrubber “(Sofnolime 797) whose function is to remove carbon dioxide from the exhaled gas.

Mares Horizon

To this, simply add a 7l tank loaded with a Nitrox blend with a minimum FO² of 30%.

Given its lightness, the addition of a ballast is essential for correct weighing. However, the appropriate steel backrest can be found online. Handcrafted which, being heavier, allows you to reduce the weight on the belt.

The Mares HORIZON rebreather is one of the so-called semi-closed rebreathers. As it partially recycles the inspired gas, therefore, the regular and constant injection of gas is necessary.

First of all, it is necessary to remember the concept of “metabolic rate” that is the quantity of oxygen consumed every minute. It is unaffected by changes in depth and is therefore constant.

While in an open circuit, gas consumption varies with depth (Boyle-Mariotte’s law), in an SCR this variation does not occur. Part of the injected O² is constantly consumed and we breathe in the new gas a few times before discharging it.

Mares Horizon
An active power SCR

The Mares Horizon is therefore an actively powered SCR with variable flow rates depending on the feed gas and the metabolic rate of its user.

This system therefore makes it possible to maintain the desired fraction of O² in the breathing loop.

The system constantly injects Nitrox into the loop and the inert gases are not metabolized. Any excess gas will be discharged from the Over-pressure Valve (OPV) with the aim of maintaining an adequate pressure within the loop.

It is important to specify that, even if the bubbles are periodically issued by the unit, their size remains negligible. They flee from the back, they can be heard, but they cannot be seen from the user.

Without diminishing the merit of those who developed the Mares Horizon SCR, it can be said that diving management with the Horizon rebreather is very similar to that with a classic open circuit tank. Indeed, they have managed to make a cutting-edge technology (rEvo) intelligible and usable, until now reserved for niche users.

In fact, regardless of learning a new equipment, like a new computer, the principle of the SCR HORIZON is not much more complex to understand than diving with Nitrox!

In light of all this, it seems undisputed that it is not necessary to be a great expert in order to understand its correct functioning.

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A bit of history

The first rebreather was designed, developed and patented in England by Henry Albert Fleuss in 1878.

At the time, this equipment was used by professional divers. For the purposes of rescue and military sabotage and anti-sabotage operations carried out during the Second World War.

In this regard, we can mention interventions that took place in 1880, such as the explosion in the Seaham coal mine or the flooding of the Severn tunnel.

During the 1950s, several SCR models entered the market. And the first “recreational” SCRs appeared at the end of this decade: Drager’s Dolphin, Azimuth or Hollis Explorer.

Main function of the SCR system

The concept is based on the principle according to which our lungs use only a fraction of the oxygen that we inspire with each respiratory act.

In fact, our body consumes only 4% of the oxygen present in the inspired air. So each breath allows you to accumulate an amount of O² necessary for several successive breaths before having to eliminate the carbon dioxide accumulated in the lung sac of our Reb.

Therefore, its main function is to recycle the exhaled CO² (in the exhalation lung bag), through the so-called “fixing system”. In order to continue its path towards the CO²-free inhalation lung sac, thus avoiding any symptoms of hypercapnia.

At the same time, by constantly adding a small amount of a gas rich in O² (minimum 5l / min) to the “breathing circuit”, it is possible to repeat the breathing act several times. With only gas present in the inhalation lung bag.

Advantages of the Horizon

In addition to a low weight, the ease of use represents the second strong point of the Horizon.

The electronic system designed with the help of rEvo technology undoubtedly makes it a life support equipment for the user. Providing it with clear and important information in relation to all its features.

From the assembly of the unit to the moment you dive, each step is supported thanks to the different “checks” that the controller, connected to it, imposes on the user. By preventing the system from starting until all checks have been carried out correctly.

Mares Horizon

The computer is easy to read and very intuitive. Fixed on the mouthpiece, right in front of the eyes, there is a HUD (visual indicator) to communicate the correct functioning of the unit by means of a green light. If the light turns red, action can be taken immediately, by switching to “Bailout” mode or in open circuit. The computer will continue to provide dive parameters and will also adapt to the gas being breathed.

Mares Horizon

This transition from closed circuit to open circuit, i.e. using the emergency tank directly, is easily carried out with a device placed on the mouthpiece, right in front of the nose and called the bailout valve (BOV).

Reassuring, right?

Mares Horizon

The design of the SCR HORIZON guarantees an ideal position: the ergonomic and soft backrest, the lumbar support and the padded harness straps are very comfortable!

The warm air that comes out of the lungs and the best diving position make breathing natural and effortless!

Mares Horizon

My Try Horizon

Well, besides these practical advantages there are certainly other more subjective ones that emerged during the test in water. Of course, it depends on your diving expectations.

As far as we are concerned, as soon as we entered the water, we were pleasantly surprised by the management of the set-up, even at a depth of a few meters. We all got used to the amazing feeling pretty quickly: not being able to use your lungs to play with buoyancy in the water.

Mares Horizon

From a physiological point of view, the fact that the inspired gas is humid and warm is very pleasant but above all prevents from overcooling of the body as well as from dehydration.

The use of nitrox, richer in oxygen, combined with the recycling of exhaled gas thanks to the SCR unit, will result in a lower production of inert gas, thus extending immersion times from 3 to 8 times.

The fraction of O² present in the inspired micelle can be changed during the dive using the computer in order to extend the bottom time or decrease the decompression time. The same will immediately notify the underwater user if the selected mixture is found to be inadequate.

Therefore, more safety, longer diving times, fewer bubbles: diving enthusiasts can undoubtedly experience diving like never before!

Freedom and silence

Finding the right position in the water came naturally to us and we felt a shared sense of great freedom… It was a great thrill to be able to get close to the shoals of saleps, an owl and many other fish, observing them without letting them escape.

A panacea for underwater photographers.

The awareness of being able to limit any discomfort related to our presence towards marine fauna and flora has allowed us to enjoy the time spent underwater better and more peacefully.

Mares Horizon

Undoubtedly, by studying and learning alternative ways of practicing scuba diving, the mastery of the techniques as well as one’s scientific knowledge related to it are improved. Furthermore, awareness of the situations in which we find ourselves is increased, thus increasing our safety in the water.

Thanks to the opportunity of the “TRY HORIZON”, a world of silence has opened up for us, in which we have been enveloped by a wonderful feeling of freedom and harmony with the environment.

Mares Horizon

The unusually long time spent in the water, in a safe way but above all in full respect of its inhabitants, will certainly allow the carrying out of many activities: underwater photography, the study of ecosystems, while contributing to the protection of the sea also through interventions of collection of “marine litters” to which we are very sensitive.

I am convinced that new “horizons” are opening up for female diving, but not only! And we, who we represent, the other side of diving, the unprofessional but nonetheless passionate and involved in what happens underwater, are ready to embark on this new journey full of beautiful projects for our sea and ours greatest happiness.

Mares Horizon

If someone had said, at the time, to the 14-year-old girl who dived in the coves near Marseille and the Island of Frioul, without a BCD and with decompression tables of plasticized paper attached to the tank harness: “in 30 years you will dive with a machine that does not make bubbles ”… I would never have believed it!

I think our looks speak for themselves and there is nothing more to add otherwise …….
see you soon for new adventures without bubbles!

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See also

La mia estate subacquea con rEvo