A device is provided for repairing a damaged location in an underwater region of a wall of a vessel or pool, in particular in the region of a wall of a pool of a nuclear reactor plant. The device includes a guiding system, which can be attached along a side wall at a distance therefrom and can be fixed thereto, for guiding a carriage which can be made to move in a longitudinal direction of the guiding system. Arranged on the carriage is a displaceably mounted holder for a repair support, which can be placed with an adhesive surface against the wall region containing the damaged location. With such a device, wall regions that are at a great depth and can only be accessed through narrow gaps can be repaired quickly and reliably.