Mercedes Gleitze wore a Rolex Oyster watch during her historic swim across the English Channel in 1927. After more than 10 hours in the cold waters, the watch remained in perfect working condition, showcasing its waterproof capabilities. This achievement led to Gleitze becoming the first Rolex Testimonee, a title used by the brand for its ambassadors, as Rolex founder Hans Wilsdorf promoted her feat in a full-page advertisement in the Daily Mail.