The present invention regards an apparatus for unwinding flexible cables on seabeds, which comprises: two first towers (2), each provided with a corresponding first vertical guide seat (5), two second towers (6), each provided with a second vertical guide seat (7), and two hub-holder groups (8), each of which slidably constrained to the second guide seat (7) of the corresponding second tower (6) and carrying, rotatably mounted thereon, a corresponding hub (3). Each second tower (6) can be moved between a first operating configuration, in which the second tower (6) is slidably constrained in the first guide seat (5) of the corresponding first tower (2), and a second operating configuration, in which the second tower (6) is arranged outside the first guide seat (5) of the corresponding first tower (2).