The combination of the sole (1)--equipped in the upper front-middle portion with the broad shaped cavity (2) and with the thin duct (3) therewith said broad shaped cavity (2) is brought in communication with the outside through the unidirectional valve (4)--of the stretching structure (5) with high change in volume implemented with flexible material with high elasticity, and of the insole (6) made of waterproof material equipped both with deformation (7) apt to cooperate with the broad shaped cavity (2) in the sole (1), to originate, under the action of the stretching structure (5), a pad-like projecting shaping, both with one or more holes (8), at said deformation (7) and in a position so as to be clogged by the foot during walking.