On March 11, 1986, the R/V Noroit, a research vessel belonging to IFREMER (Institut Francais de Recherche, pour l'Exploitation de la Mer, Paris), was on station in the northeast Atlantic Ocean (46°54′N, 11°14′W). The crew were performing a deep conductivity‐temperature‐depth (CTD) cast (water depth 4750 m) as part of a survey of abyssal circulation in that region. The towed CTD instrument unit was 120 m from the bottom when the cable ruptured, resulting in the loss of the instrument and 4788 m of cable. The cause of the cable failure was quickly diagnosed as corrosion on a rarely used part of the cable.