Reservoir Hydrosphere

The Reservoir Hydrosphere is available in three variants, the Blackfin, the Blue Hole and the Air Gauge, each presented in its own distinctive colourway. These models represent Reservoir’s first foray into diver’s watches. A unidirectional bezel, 250m water resistance and a helium valve are just some of the specification highlights for subaquatic types. Angus Davies examines this new watch in close detail.

This detailed review of the Reservoir Hydrosphere includes live images, specification details and pricing.

Reservoir Hydrosphere

In the sphere of horology, it is difficult for a brand to differentiate its products from its competitors’ models. The watch-buying public are accustomed to the idea of watches endowed with two hands. A sprinkling of complications, a dash of alternative case materials or a soupçon of silicium are often used to whet the appetite of budding horophiles seeking something different.

A few years ago, Reservoir, a French watch brand, showcased a small array of highly original timepieces. Each watch was designed to emulate an instrument such as a car’s rev counter, an aviation-inspired dial or a submarine depth gauge.

Recently, the innovative Maison unveiled a new watch, a diver’s model named the Reservoir Hydrosphere. This watch subscribes to some of the elements which have led to the commercial success of its forebears, however, there are some new features which make it stand out from the crowd.

Reservoir Hydrosphere

Intended to resemble a diver’s pressure gauge, the Reservoir Hydrosphere is offered in three variants, the Hydrosphere Blackfin (black dial option), the Hydrosphere Blue Hole (blue dial option) and the Hydrosphere Air Gauge (white dial option).

The dial

Often, when I look at a selection of models, one particular reference stands out and this is the case with the Reservoir Hydrosphere. Personally, I prefer the white dial option, owing to its notably clear display.

Reservoir Hydrosphere

Consistent with other Reservoir models, the Hydrosphere features a jumping hour display, positioned in the lower portion of the dial. The hour value is presented in black on a white disc and enlarged via a magnified lens.

A lone hand follows an arcing trajectory from 8 o’clock to 4 o’clock, indicating the minutes from ’00’ to ’60’. The minute hand is white with a black border. When the minute hand reaches ’60’ it returns to ’00’ with breathtaking alacrity.

A prerequisite of any diver’s watch is that the minute hand should be clearly distinguishable from the hour hand. By employing a jumping hour display, Reservoir has delivered a superb means of delineating the hours from the minutes.

Reservoir Hydrosphere

The unidirectional ceramic rotating bezel is marked with two scales as the minute track spans 240° instead of the customary 360°. The bezel is marked ‘before and after the retrograde minute hand’s return’, employing both blue and red hues.

A power-reserve indicator is positioned in the lower portion of the dial. Once again, this function employs blue and red tones, together with a white marker, to display the state of wind. A diver’s bottle pressure gauge reveals the content pressure of the cylinder, expressed in bar. Reservoir has marked the dial of the Hydrosphere with the maximum water resistance, also expressed in bar, together with metres, again mimicking the design of an instrument display.

Clearly, when using a watch as a diving tool, safety is of paramount importance. In order to convey to the wearer that the watch is operational, a central disc, positioned at the fulcrum of the dial, continuously rotates.

The case

Measuring 45mm in diameter, the Reservoir Hydrosphere is a leviathan. However, when worn the watch feels much smaller, courtesy of its lug-free case. The watch is supplied with a bracelet and an additional rubber strap. Both of these integrate directly with the watch head and are held steadfast with screws. The bracelet or strap project downwards, perpendicular to the watch head, readily enveloping the wrist.

Reservoir Hydrosphere

The case and bracelet are formed of 316L stainless steel. The latter item is presented in a 3-rows design. There is no hint of sharpness to any facet of the case or bracelet. A sense of quality pervades this watch.

Consistent with diver’s watch custom, the case back is solid and, in this instance, features a screwed back. This, together with a screw-down crown, featuring black coating, provides an impressive maximum water resistance of 250m. While there are watches which proffer greater water resistance, they do have a tendency to be bulkier.

Reservoir Hydrosphere

Should the wearer wish to partake in saturation diving, the Reservoir Hydrosphere is fitted with a helium valve. Working in an environment rich in helium gas can lead to the gas entering the diver’s watch. On returning to the ocean surface, the build up of gas within the watch can sometimes cause the sapphire crystal to pop off. The addition of a helium valve mitigates the risk of this happening.

The movement

While Reservoir is a French company, its watches are made in the watchmaking capital of Switzerland, La Chaux-de-Fonds. At the heart of the Hydrosphere is the venerable ETA 2824-2 caliber, a movement known for its reliability.

Reservoir has mounted its own 124-piece patented module to the movement. The module is responsible for the jumping hours and retrograde minutes display. Normally, jumping hours and retrograde minutes devour energy, resulting in low stated power-reserve figures. However, when contrasted with a standard ETA 2824-2 with a typical power reserve of 42 hours, the 37 hours of autonomy quoted by Reservoir is quite impressive.

I was unable to appraise the movement finishing owing to the solid caseback.

Reservoir Hydrosphere

The balance oscillates at 28,800 VpH (4Hz). The patented module is equipped with a safety device which prevents the wearer rotating the minute hand before ’00’ and, in so doing, harming the movement. While Reservoir is a comparatively small company, it has clearly expended much time ensuring its models prove reliable.

Closing remarks

There are several pre-requisites for diver’s watches. The wearer should be able to easily distinguish the minute hand from the hour function as they will rely on the minute hand when performing a dive. Furthermore, a diver’s watch should feature a uni-directional bezel and impressive water resistance. With regards to these subaquatic necessitates, the Reservoir Hydrosphere ‘fits the bill’.

For most diver’s, save for some hard-core professional types, a helium valve is probably not necessary. However, the world of high-end watches is overflowing with attributes few will seldom need. The inclusion of a helium valve is just one more feature that enriches the ownership experience.

I must admit that I am not a diver and yet I am frequently drawn to this genre of watch. I appreciate the robustness of a diver’s watch and the generous scale of each indication. However, most of all, I like being able to shower or swim in my watch, safe in the knowledge its internal organs will remain dry. In simple terms, a diver’s watch is a very practical ownership proposition.

The Reservoir Hydrosphere upholds said practicality but also imparts a wonderful sense of theatre. After an hour is complete, the numeral, shown at the base of the dial, disappears and the next value jumps into view. The retrograde minutes advance along an arcing path until they reach their ultimate destination and then return to the point of origin and relive the moment once more.

Lastly, Reservoir has shrewdly incorporated influences from a diver’s bottle pressure gauge without marring lucidity or eye-appeal. The Maison has created another gem that is worthy of exploration.

Further reading

Technical specifications

  • Model: Reservoir Hydrosphere
  • Reference: RSV03.HY/130-12 (Blackfin); RSV03.HY/130-32 (Blue Hole); RSV03.HY/130-21 (Air Gauge)
  • Case: Stainless steel 316L; diameter 45mm; water resistance 25 ATM (250 metres); sapphire crystal to the front and solid caseback
  • Functions: Jumping hours; retrograde minutes; power-reserve indicator
  • Movement: ETA 2824-2automatic movement; frequency 28,800 VpH (4Hz); power reserve = 37 hours
  • Strap: Supplied on stainless steel bracelet 316L with blade folding clasp & supplied with additional rubber strap
  • Price – £3,900 (RRP as at 29.4.2019)

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