When it comes to diving watches, Rolex stands as an undisputed titan in the watch industry. Its Submariner and Sea-Dweller lines are both critically acclaimed and highly sought-after in the market.
As early as the 1920s, the Swiss brand had already developed the waterproof Oyster case. In 1927, British swimmer Mercedes Gleitze wore a Rolex Oyster wristwatch during her historic attempt to swim across the English Channel. Even after spending ten hours in the water, the watch still functioned perfectly, not in the least affected. This feat cemented Rolex's reputation for waterproof watches.
Nearly a century later, the Rolex Oyster that accompanied Gleitze for years will go under the hammer at Sotheby's Geneva this coming Sunday (9 November), carrying an estimate of over CHF 1 million (US$1.25 million).
Lot 134 | 'The Companion Oyster' Mercedes Gleitze Rolex Oyster | An extremely early pre-production prototype of the world’s first practical waterproof wristwatch, Oyster reference 34075, with Glasgow import hallmarks for 1926/1927
Manufactured in 1926
Estimate Upon Request (over CHF 1 million)
Auction House: Sotheby's Geneva
Sale: Important Watches I
Date: 9 November 2025 | 11 am (Geneva local time)
Mercedes Gleitze was born in 1900 to a family of German immigrants in the southern English seaside city Brighton. She was not an athlete who had received swimming training since childhood. Thanks to the bilingual environment of English and German where she grew up, she worked as a secretary and stenographer after graduation.
Gleitze enjoyed swimming in the River Thames in her spare time, gradually building remarkable stamina that allowed her to swim for hours on end. In 1923, she swam continuously in the Thames for 10 hours and 45 minutes, setting the women's record for the longest uninterrupted swim in the Thames.
Her ambitions soon grew bolder. She set her sights on the English Channel, the stretch of sea between England and France. On her eighth attempt on 7 October 1927, she achieved the feat in just 15 hours and 15 minutes, becoming the first woman to swim across the English Channel.
Her achievement, however, was challenged by another female swimmer. Although the allegations were later proven unfounded, Gleitze decided to silence all doubts through actions by attempting the English Channel crossing once more.
Mercedes Gleitze
The story of Gleitze was made into the film Vindication Swim last year
This "vindication swim" attracted extensive media coverage, with some British newspapers even sending reporters on boat to film the entire journey. Among those who took notice was Hans Wilsdorf, the founder of Rolex. Recognising an ideal opportunity to showcase the waterproof Oyster case, he invited Gleitze to wear a Rolex during her attempt.
Just two weeks later, on 21 October 1927, Gleitze entered the Channel once more. This attempt, however, was thwarted by unforeseen weather conditions: the water of the English Channel was colder than anticipated, with patches of ice forming in parts of the sea. After swimming valiantly for more than ten hours, she was forced to abandon the attempt.
Even so, her perseverance in such adverse conditions earned her widespread acclaim. The Rolex Oyster she wore around her neck continued to function perfectly after ten hours in freezing seawater. This feat brought Rolex's waterproof timepieces considerable renown.
Gleitze thus became an ambassador of Rolex, pioneering the trend of appointing athletes as brand ambassadors before it became a common practice in the watchmaking industry.
A large number of media personnel got on a boat to witness the crossing of the English Channel by Gleitze
After enduring for ten hours, Gleitze was taken out of the water
Rolex launched a full-page advertisement for its Oyster wristwatches in Daily Mail, making Gleitze its promotion ambassador
The Oyster case refers to a waterproof sealed case. With a screw-down case back and bezel, along with Rolex's patented screw-down winding crown, the case achieves complete water resistance. The wearer may screw down the crown to lock the case.
The watchcase, which seals as tightly as an oyster shell and operates freely underwater, inspired its name Oyster.
Building upon the innovation of the Oyster case, Rolex went on to develop watches that are capable of enduring more extreme conditions over the decades. Among those was the Deep Sea Special, a diving watch capable of descending nearly 11 kilometres into the Mariana Trench – a record-setting achievement for both humans and watches at the time.
Subsequently developed, the Submariner and Sea-Dweller diving watch lines achieved both critical and commercial success, solidifying Rolex's standing in the diving watch market.
It is engraved on the case back that the watch was worn by Gleitze during her crossing of the English Channel on 21 October 1927
The octagonal 9K yellow gold case of Gleitze's Oyster measures 31 x 27mm. Its case back is engraved to confirm that the watch was worn by Glitze during her crossing of the English Channel on 21 October 1927.
This watch remained in Glitze's possession until her passing. In 2000, her descendants released it to the market, where it sold at Christie's London for £17,037.
Twenty-five years later, the wristwatch will once again come under the hammer with an estimate of CHF 1 million (around £900,000) – an appreciation of over 52 times its original value.