Delma released the Shell Star in 1975, its first professional dive watch. The collection has improved over time with upgraded materials and designs, and the latest Shell Star Decompression Timer includes comprehensive decompression tables on the dial. The tables are based on research from the 1950s and 1960s by Swiss dive pioneers Hannes Keller and Albert Bühlmann, who took altitude into account for optimal decompression techniques. The tables allow saturation divers to calculate the number and duration of decompression stops (if required) based on the depth and length of the dive.
The stainless steel case is somewhat oversized for a professional diver at 44mm in diameter and 13.8mm in height. The large diameter allows for excellent legibility underwater and is necessary for the complex decompression tables that could otherwise become impractically small. The unidirectional rotating bezel has a detailed 60-minute scale and comes in black, blue or orange anodized aluminium. The screw-down crown is fully guarded and there’s a helium escape valve at 9 o’clock, all necessary for deep-sea exploration. There’s an exhibition case back with a mineral crystal that’s rare for a diver that can descend to 500 metres. The dial is protected by a sapphire crystal with an anti-reflective coating. There are two 24mm strap options – a three-link stainless steel bracelet with deployant clasp/push buttons and a rubber strap in blue or black. The case itself is based on other Shell Star models, including a previous limited edition watch from 2018, the Shell Star Black Tag Limited Edition.
The specialized dial is unique for a Delma Shell Star diver, but it’s not a first in this price range. We went hands-on with the Mido Ocean Star Decompression Timer 1961 Limited Edition last year with a comparable decompression dial and 200-metre water resistance rating, and a turquoise variant recently debuted as well. That said, DELMA’s version is well-executed and unique. It’s designed for diving from 0 to 700 metres above sea level based on the aforementioned mid-century research, which remains a standard today. A vertical scale at 12 o’clock is for diving depth in both feet and metres and shows if the dive is within the no-decompression limit (NDL) or if decompression stops are required. Empty white squares mean that the dive is within the NDL, while coloured squares show the number and duration of decompression stops.
A black or blue dial is available (the blue dial comes with the blue bezel) and the hands and applied indices have lume. The seconds hand has DELMA’s retro spade style and the orange indices and railway track also go back to early Shell Star divers. A date window sits at 3 o’clock.
Powering the collection is the Sellita SW200 automatic with a custom rotor. It’s based on the ETA 2824 and has 26 jewels, beats at 28,800vph (4Hz) with a 38-hour power reserve. Functions include central hours, minutes, hacking seconds and date.
Prices for the DELMA Shell Star Decompression Timer are typical for the brand, starting at CHF 1,100, EUR 1,200 or USD 1,290 for the rubber strap and CHF 1,150, EUR 1,250 or USD 1,350 for the steel bracelet. Not bad for such a capable and unique dive watch. For more information and to make a purchase, visit DELMA’s website.