Abstract: A method, using a crane-equipped depot ship, for automatically repairing an underwater pipeline even if installed at great depth, comprising substantially the following steps: cutting off the damaged pipe piece by a single working module which, lowered onto the sea bed by a crane and clamped about said pipeline, removably supports the cutting apparatus; removing the concrete from the facing ends of the cut pipeline by said single working module which removably supports the removal apparatus, this being provided with an expansion-centering head; installing connectors by a sonar head alignment apparatus removably supported by said working module; and installing the replacement pipe piece by said working module using a reference and guide apparatus clamped about said ends of the pipeline. Specific apparatus for implementing the method are also described.