Diving watches are notoriously bulky affairs, and it isn't just for looks. The heavy construction and thick crystals are necessary to keep the timepiece from imploding in deep waters. The Ressence Type 5 recreational diving watch takes a different approach by adopting a shape inspired by sea turtles and filling it with oil, which not only makes it more pressure resistant, but also makes it readable underwater from any angle.

If you've ever gone scuba diving, you may have noticed that dive watches are often very difficult to read due to what's called "total internal reflection." Underwater, the refraction in an air-filled space behind watch crystals turn them into mirrors, so to read the time it's necessary to look at the dial straight on. Since keeping one eye on the time is vital for safe diving, it's a common and constant irritation.

By immersing the entire movement and dial in 37.5 ml of oil, the Ressence Type 5 design eliminates the refraction and reflection, so the dial can be read from any angle. In addition, the oil provides a magnifying effect and gives the illusion that the crystal isn't there. It's a solution that's been used for some digital watches, but Ressence says that this is a first for a mechanical watch.

Another advantage is that since oil isn't compressible, the Type 5 eliminates the need for a heavy case and crystal. The oil also lubricates all the components and suspends the parts, so they're effectively working in zero gravity. This means less power is needed to drive the movement and it's more accurate.

The Type 5 is sealed in a 46 x 15.5 mm titanium grade 5 case rated to 10 ATM with domed, anti-reflective, sapphire crystals front and back. Inside, there are two sealed chambers. The upper one contains the movement and dial and is filled with oil, while the lower one contains the counterweight for the self-winding mechanism. There is no physical connection between the weight and the movement. Instead, micro-magnets transmit the power from the spinning weight to the mainspring. Meanwhile, the fields are engineered to remain close to the magnets, so they don't interfere with the movement.

The 60-jewel Ressence Orbital Convex System (ROCS) 5 movement is made of 142 components with a 36-hour power reserve, which drives a three-dimensional revolving bridge architecture. There's no crown for setting or winding – Ressence has improved water resistance by using the sapphire case reverse for both functions. When set to "lock" the internal gasket is compressed. Switching it to "set" allows the back to turn, which sets the watch and winds it simultaneously. In addition, the arrangement allows for an ergonomic fit for lefties and righties.

In addition, the movement has a compensating bellows system that extends and compresses to counteract the expansion and contraction of the oil in extreme temperatures from minus 5º to 55º C (23º to 131º F).

The convex titanium dial of the Type 5 shows that there's more to it than just oily clockwork. It has a main hand for displaying minutes and three eccentric biaxial subdials for the hours display, a runner display of 90 seconds, and a thermal gauge. The latter is a mechanical gauge that displays a readout of a combination of the oil temperature and that of the wearer's wrist.

The party piece of the Type 5 is that the dials aren't static, but revolve about the main disc, which Ressence claims produces a more intuitive readout. In addition, the indicators are filled with blue and green Superluminova for day and night use.

The Ressence Type 5 is available for €26,250 (US$28,855).

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