In the history of Rolex, Mercedes Gleitze occupies an unusual position. Her name is synonymous with the early Oyster, but one of her most remarkable achievements took place much closer to home for Watch & Bullion.
On 5 April 1928, after a series of failed attempts, Gleitze entered the water off Tarifa and spent 12 hours and 50 minutes fighting the currents of the Strait of Gibraltar. When she reached Punta Leona on the Moroccan coast, she became the first known person to swim the Strait.
The Mercedes Gleitze Gibraltar swim happened less than six months after the episode that had helped establish the Rolex Oyster as a serious waterproof wristwatch.
It creates an unusually direct connection between early Rolex history and the waters surrounding Gibraltar, although the surviving evidence requires one important distinction: the Rolex is documented during her English Channel swim, not during the successful Gibraltar crossing.
Before Gibraltar came the Rolex Oyster
Rolex introduced the Oyster in 1926. Hans Wilsdorf had spent years trying to solve a basic problem with the emerging wristwatch: protecting a mechanical movement from water, dust and everyday contamination without making the watch impractical to use.
The Oyster case used a screw-down bezel, case back and winding crown to create a hermetically sealed watch. Rolex described it as the world’s first waterproof wristwatch.
The name itself was deliberate. Wilsdorf later explained that he chose “Oyster” because, like the shellfish, the watch could remain underwater while protecting what was inside.
Contemporary Rolex material also compared the case to an oyster that shut out dust and other impurities.
Engineering the case was only part of the task. Wilsdorf also needed to demonstrate that the idea worked outside a workshop.
Mercedes Gleitze provided that opportunity. On 7 October 1927, after seven unsuccessful attempts, she became the first British woman to swim the English Channel. Her crossing from France to England took 15 hours and 15 minutes.
The achievement was quickly complicated by another swimmer’s fraudulent claim to have crossed the Channel in a faster time.
Although that account was exposed as a hoax, doubts had already been cast over Gleitze’s own record. She decided to return to the water.
The Vindication Swim and the watch that survived it
Her attempt on 21 October 1927 became known as the Vindication Swim. This time Gleitze carried a gold Rolex Oyster supplied by Wilsdorf.
The conditions were severe. After more than ten hours in exceptionally cold water, she was forced to abandon the crossing.
The swim nevertheless vindicated her reputation, while the watch provided Wilsdorf with something commercially valuable: a real-world demonstration of the Oyster’s resistance to prolonged immersion in salt water.
Rolex’s own historical record states that the watch emerged from the Channel in perfect working order. Wilsdorf followed the event with a full-page Daily Mail advertisement proclaiming the Oyster’s performance and helping establish what Rolex would later call the Testimonee concept.
That formula became central to the company’s identity. Rather than treating water resistance as an abstract technical specification, Rolex associated its watches with swimmers, explorers, racing drivers, aviators and mountaineers who could test them in demanding conditions.
Then Mercedes Gleitze turned towards Gibraltar
Within weeks, Gleitze had moved her attention south to the Strait of Gibraltar.
On a map, the crossing can appear deceptively straightforward.
Europe and Africa are separated by only a relatively narrow body of water, but a swimmer must contend with powerful currents created by the interaction of Atlantic and Mediterranean waters, changing wind conditions and a route that can lengthen considerably once drift is taken into account.
Gleitze discovered that repeatedly. Her first attempt came in December 1927, initially trying the crossing from the North African side.
Further attempts followed in January, March and April 1928. Contemporary reporting records one January effort in which she was caught in a whirlpool and came close to drowning.
She kept returning. The successful crossing was her sixth attempt.
From Tarifa to Morocco
The documentary record preserved by the Mercedes Gleitze archive dates the successful swim to 5 April 1928.
The crossing was organised with the Mayor of Tarifa and the military commandant of the Tarifa garrison, while two sailing vessels accompanied her across the Strait and a formal witness statement was produced afterwards.
The date is worth recording carefully because 6 April is repeated in a number of later accounts. The surviving Act of Requisition and Gleitze chronology give 5 April, while subsequent newspaper coverage appeared on the following days.
Gleitze entered the water at Tarifa at approximately 7.50am and headed towards Punta Leona on the Moroccan coast. Contemporary newspaper reporting records her reaching land at 8.40pm after 12 hours and 50 minutes in the water.
It was an unusually long time for what appears geographically to be a short crossing. The explanation lies in the Strait itself. Strong and changing currents carried Gleitze away from a direct line, turning the attempt into a considerably longer swim than the straight-line distance between the two shores suggests.
When she reached Morocco, Gleitze had become the first known swimmer to cross the Strait of Gibraltar successfully.
The International Swimming Hall of Fame records the achievement among the first-ever swims of her career, while today’s Strait of Gibraltar Swimming Association traces the organised history of the crossing back to Gleitze’s attempts.
Was she wearing the Rolex in Gibraltar?
This is where the Rolex and Gibraltar stories need to be separated carefully.
There is clear documentary evidence that Gleitze carried a Rolex Oyster during the Vindication Swim in the English Channel. Rolex’s archives, contemporary reporting and the surviving watch itself all support that account.
We have not found equivalent primary evidence establishing that she wore the Oyster during the successful Gibraltar crossing on 5 April 1928.
It is therefore misleading to describe the Mercedes Gleitze Gibraltar swim as another documented Rolex endurance test.
The connection is chronological rather than dependent on placing the watch in the Strait: the same swimmer who had just helped demonstrate the practicality of Wilsdorf’s waterproof Oyster went on, within months, to establish the first recognised swimming route between Europe and Africa across Gibraltar.
That distinction makes the history stronger, not weaker. It allows the two achievements to be understood on their own terms without turning an association into a claim that the evidence does not support.
The Companion Oyster
The watch associated with Gleitze’s Vindication Swim survived. Sotheby’s describes the so-called Companion Oyster as an early 9-carat gold example with an octagonal case and Glasgow import hallmarks for 1926/27.
Its case back carries an inscription commemorating Gleitze and the Vindication Channel Swim of 21 October 1927.
The watch remained connected to Gleitze and later passed through her family before appearing at Christie’s in 2000. In November 2025, it returned to auction at Sotheby’s in Geneva, where it sold for CHF 1,392,000.
The price reflects more than the rarity of an early Oyster. The watch sits close to the point at which waterproofness moved from being a technical watchmaking problem to one of the defining ideas behind Rolex.
Why the Mercedes Gleitze Gibraltar swim matters
Mercedes Gleitze appears regularly in histories of Rolex, usually through the familiar sequence of the Oyster, the English Channel and Wilsdorf’s Daily Mail advertisement. Her connection with Gibraltar receives far less attention.
Viewed from the Rock, the chronology is remarkable. In October 1927, she was helping demonstrate a new idea in wristwatch construction in the English Channel.
By April 1928, she was in the waters immediately beyond Gibraltar attempting something no recognised swimmer had previously achieved.
After six attempts, she crossed the Strait.
The Rolex did not make that crossing historically significant, nor does the story require us to place the watch in waters where the surviving evidence does not.
The connection is more interesting than that. One of the formative figures in the history of the modern waterproof wristwatch also wrote an important early chapter in the sporting history of the Strait of Gibraltar.
For collectors researching an older Rolex of their own, our Rolex Serial Number Lookup provides an approximate production period from the watch’s serial number.
Sources and further reading
The documentary record for the successful Gibraltar crossing, including the translated Act of Requisition and witness statement, is preserved by the Mercedes Gleitze archive.
The International Swimming Hall of Fame records Gleitze as the first swimmer to complete the Strait, while the British Newspaper Archive reproduces contemporary reporting of her attempts and successful crossing.
For the watchmaking side of the story, Rolex documents the Oyster and Gleitze’s 1927 Channel swim in its official Oyster history. Sotheby’s has also documented the surviving Companion Oyster and its 2025 auction.
Further reading from the Watch & Bullion Journal: King Harald’s Rolex GMT-Master: Six Decades on the Wrist, Rolex Bracelets Made Outside Switzerland, and Albert Einstein Patek Philippe: Einstein Watch Myth Explained.
