The Isle of Mull ferry was withdrawn from service after it started taking on water.
After completing a sailing from Oban to Craignure the boat was cancelled as a precaution on Wednesday.
A CalMac spokesman said: “The MV Isle of Mull reported a very small amount of water ingress into one of its ballast tanks and was withdrawn from service as a precaution after completing the 2.15pm sailing to Craignure on November 1.
“On inspection by divers after returning to Oban the problem was identified.
“A temporary timetable was put in place while repair work was carried out and the vessel returned to service at 2pm on November 2.”