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 said carriage and serves to lock the abandonment chain while lowering said carriage and said top end of the pipe at the end of the chain, said second locking device then being in an open position at the base of said tower. Thereafter, said abandonment chain is locked at the low portion of the tower with the help of said second chain-locking device, with the first chain-locking device being in the open position while the carriage is being raised.