A device and a method for lowering or raising the end of an undersea pipe between a vessel and the sea bottom by a carriage moving along an inclined J-lay tower and co-operating with chain-locking devices connecting the top end of the pipe to a storage area by passing over a deflector sheave secured to said carriage. A first chain-locking device is secured to the carriage and serves to lock the abandonment chain while lowering the carriage and the top end of the pipe at the end of the chain, a second locking device then being in an open position at the base of the tower. Thereafter, the abandonment chain is locked at the low portion of the tower with the help of the second chain-locking device, with the first chain-locking device being in the open position while the carriage is being raised.