Fifty Fathoms is a line of dive watches from Blancpain.

The French military dive unit required a specialized timepiece for combat divers after World War II but no manufacturer stepped forward with a watch that would meet their demands. Blancpain CEO Jean-Jacques Fiechter was approached, being an avid diver, and agreed to take up the challenge. The requirement was for, “a watch with a black dial, large, bold numerals and clear markings, as well as an outer rotating bezel … to be able to align this bezel with the large minute hand, in order to easily know our remaining oxygen time … we wanted all those markers to clearly glow in the dark.” This has remained the prototypical dive watch to this day.

Blancpain built the first Fifty Fathoms watch in 1953, meeting all these requirements. This was the same year that Rolex introduced their classic Submariner watch. It was highly unusual in design for the time The case was huge at 42 mm diameter and featured large molded lugs. It was waterproof to a depth of 50 fathoms (91.45 meters), which was the maximum depth reachable on the oxygen tanks of the day. It featured a screwed-on caseback and double O-rings around the crown stem to prevent water infiltration, though Blancpain did not specify a screwed-down crown to avoid infringing on a Rolex patent. The movement was automatic and anti-magnetic so the crown could be left in place as much as possible.

The dial is black and features large markers at all 12 hours. 12 00 is marked with a large arrow, 3, 6, and 9 are marked with bars, and the other hours with dots, making it easy to read even in darkness. Some civilian models also featured Arabic numerals at 3, 6, 9, and 12. Military versions featured radium luminescence, while civilian versions used conventional luminescent paint and the famous “No Radiation” logo. Some Fifty Fathoms watches also featured a humidity detector painted on the dial which turns blue if it gets wet.

The unidirectional bezel was unique to the Fifty Fathoms and its look is iconic. It featured luminescent markings in a large epoxy ring A diamond marks 0, and bars sit between markers at 15, 30, and 45. Although modern 50 fathoms have “minute” bars between 0 and 15 for dive timing, this is not part of the original design.

A special Bathyscaphe model was released as well in the 1950s, featuring a large “12” and three arrows replacing the arrow and bar markers on the dial. It was smaller than the regular Fifty Fathoms at 35 to 38 mm and intended to be worn inside a submersible rather than while diving.

Soon Blancpain's Fifty Fathoms watch was in use by the naval divers of the United States (with Tornek-Rayville signed dials), Germany, Spain, Poland, Czech, and Israel, along with civilian divers like Jacques Cousteau. The Fifty Fathoms features prominently in Cousteau's breakout 1956 hit, The Silent World, which brought recognition to this special timepiece. Soon, most other Swiss watchmakers were launching their own dive watches with a similar look.

Casual divers loved the Fifty Fathoms as well, and it was sold in dive shops (like Aqualung, which would get its own signed models) rather than jewelry or watch shops. Lip retailed the Fifty Fathoms to consumers in France, though they had turned down the opportunity to make the watch in the first place. Like many watches that have proved collectible today (especially dive watches from Panerai and Rolex), historic Fifty Fathoms watches often show signs of wear, repair, and modification.

Production of the Fifty Fathoms line ended in the 1970s as quartz movements became popular and lower-priced competitors like Seiko took up the challenge of producing tool watches. Blancpain ceased producing watches for two decades, with Omega taking over their factory as part of SSIH, though a few were produced into the 1980s for military customers. The Blancpain brand restarted in 1982 under Jean-Claude Biver and Jacques Piguet, but they did not bring the Fifty Fathoms back into production, wishing to concentrate on luxury models instead.

Blancpain was sold back to Swatch Group in 1992 with permission to return to sports watches. In 1997, Blancpain reintroduced the Fifty Fathoms brand on a luxury watch with relief numerals at 5 minute increments on a metal bezel rather than the classic inset. This was part of a “Trilogy” of watches for land (a GMT), air (the Air Command) and sea (the Fifty Fathoms). This new watch was water resistant to 165 fathoms (300 meters) but kept the classic name. The Trilogy was revived in 1999 as the limited “Concept 2000” series with carbon fiber reinforced rubber bezels, crowns, and pushers. Another limited edition Fifty Fathoms added the first-ever perpetual calendar version.

Blancpain returned to the classic Fifty Fathoms look with a limited edition series in 2003 to commemorate the 50th anniversary of the watch. The case was 40.3 mm and was water resistant to 300 meters but the classic dial and bezel was recreated. Sold in three editions of 50 watches each, these sold out almost immediately. They featured F. Piguet's Cal. 1151, a double barrel movement with 100 hours power reserve. These anniversary models had numerals at 3, 6, 9, and 12 and a simplified bezel with numbers only at 15, 30, 45 and bar markers in between.

The 2007 Fifty Fathoms returned to the classic look, this time with a domed sapphire ring over the bezel. These used Blancpain's in-house triple-barrel Cal. 1315 for 5 days power reserve, which would go on to serve in most modern versions. Modern FIfty Fathoms watches are water resistant up to 300 meters but retain the historic name and look, though the case has been enlarged to 45 mm to accommodate a multi-part soft iron inner case for magnetic resistance. The modern Fifty Fathoms features Arabic numerals at 3, 6, 9, and 12 like some original civilian models, and arrow markers at the other hours. A date window is inset between the markers at 4 and 5.

Complicated Fifty Fathoms watches appeared shortly after. The Blancpain Fifty Fathoms Chronographe Flyback adds a chronograph complication for the first time, with special water resistant pushers. The Blancpain Fifty Fathoms Tourbillon has a transparent case back to display the flying tourbillon inside. Annual and perpetual calendar models also appeared.

Blancpain diverged from the Fifty Fathoms name with the appropriately-named 500 Fathoms, launched in 2009. Equipped with a helium escape valve, the 500 Fathoms model is water resistant to 100 bar (1000 meters) and the titanium case measures 48 mm in diameter. A GMT version was introduced shortly after.

Blancpain introduced the X Fathoms in 2012 with a massive 55 mm diameter, 24 mm thick titanium case. In addition to time the automatic movement has a retrograde 5 minute counter for decompression timing. The X Fathoms also features a mechanical depth gauge with two scales and maximum depth memory along with a decompression valve. The dial features Arabic numerals at 3, 6, 9, and 12, with 0-90 meter markings inside for the depth gauge and 0-15 meter markings for shallow depth measurement outside. The 5-minute counter has its own scale and pointer at 10 30.

Another expansion of the line came at Baselworld in 2013 with the Fifty Fathoms Bathyscaphe, a return to the flat bezel look in a smaller 43 mm case. Similar to the classic Bathyscaphe, this is more of a daily wear watch though no less functional. However it does not feature the Arabic 12 or arrow markers of the original Bathyscaphe. In 2017, Blancpain released a smaller 38 mm version of the Bathyscaphe.

• Blancpain Fifty Fathoms Automatique Ref. 5008, 5015 - Cal. 1315, water resistant to 30 bar
• Blancpain Fifty Fathoms Automatique Grande Date Ref. 5050 - Big date at 6 00, water resistant to 30 bar
• Blancpain Fifty Fathoms Chronographe Flyback Ref. 5085 - Cal. F185, flyback chronograph, water resistant to 30 bar
• Blancpain Fifty Fathoms Chronographe Flyback Speed Command Ref. 5785 - Cal. F185, flyback chronograph, water resistant to 30 bar
• Blancpain Fifty Fathoms Chronographe Flyback Quantième Complet Ref. 5066 - Cal. 66BF8, flyback chronograph, full calendar, water resistant to 30 bar
• Blancpain Fifty Fathoms Tourbillon 8 Jours Ref. 5025 - Cal. 25A tourbillon, water resistant to 30 bar
• Blancpain 500 Fathoms Ref. 50015 - Cal. 1315, water resistant to 100 bar
• Blancpain 500 Fathoms GMT Ref. 50021 - Cal. 5215, water resistant to 100 bar
• Blancpain Fifty Fathoms Bathyscaphe Ref. 5000 - Cal. 1315, water resistant to 30 bar
• Blancpain Fifty Fathoms Bathyscaphe 38 mm Ref. 5100 - 38 mm case, water resistant to 30 bar
• Blancpain Fifty Fathoms Bathyscaphe Jour Date Ref. 5052 - Day/date, water resistant to 30 bar
• Blancpain Fifty Fathoms Bathyscaphe Chronographe Flyback Ref. 5200 - Cal. F385, flyback chronograph, water resistant to 30 bar
• Blancpain Fifty Fathoms Bathyscaphe Quantième Complet Ref. 5054 - Full calendar, water resistant to 30 bar
• Blancpain Fifty Fathoms Bathyscaphe Quantième Annuel Ref. 5071 - Annual calendar, water resistant to 30 bar
• Blancpain X Fathoms - water resistant to 30 bar

• Depth Benefit, Watchtime, October 2013