An underwater device which is intended to be deployed in water, the device comprising: - an assembly of arms (10a, 10b, 10c, 10d, 10e) which are articulated to a support body which has a reference axis r, the arms being capable of being held in a folded configuration and being capable of being deployed as far as a deployed configuration in which the arms (10a, 10b, 10c, 10d, 10e) extend around the reference axis r, the arms (10a, 10b, 10c, 10d, 10e) being deployed by means of distal ends of the arms (10a, 10b, 10c, 10d, 10e) being moved away from the axis r, - an assembly of at least one flexion spring (14a, 14b, 14c, 14d, 14e) which is resiliently biased in flexion when the arms (10a, 10b, 10c, 10d, 10e) are held in the folded configuration and which is capable of relaxing when the arms are released from the folded configuration, the assembly of at least one flexion spring (14a, 14b, 14c, 14d, 14e) being configured and arranged so as to apply to at least one of the arms (10a, 10b, 10c, 10d, 10e), when the arms (10a, 10b, 10c, 10d, 10e) are released from the folded configuration, a thrust which causes the deployment of the arm (10a, 10b, 10c, 10d, 10e), characterised in that the flexion spring is generally biased in flexion when the arms (10a, 10b, 10c, 10d, 10e) are held in the folded configuration and generally works in flexion when the arms are released, at least one of the at least one flexion spring comprising an anchoring portion which is fixed relative to the reference axis r, and a deformable portion which becomes deformed when the flexion spring relaxes, the deformable portion being wound around the reference axis when the arms (10a, 10b, 10c, 10d, 10e) are held in the folded configuration and being unwound when the spring relaxes. - an assembly of arms (10a, 10b, 10c, 10d, 10e) which are articulated to a support body which has a reference axis r, the arms being capable of being held in a folded configuration and being capable of being deployed as far as a deployed configuration in which the arms (10a, 10b, 10c, 10d, 10e) extend around the reference axis r, the arms (10a, 10b, 10c, 10d, 10e) being deployed by means of distal ends of the arms (10a, 10b, 10c, 10d, 10e) being moved away from the axis r, - an assembly of at least one flexion spring (14a, 14b, 14c, 14d, 14e) which is resiliently biased in flexion when the arms (10a, 10b, 10c, 10d, 10e) are held in the folded configuration and which is capable of relaxing when the arms are released from the folded configuration, the assembly of at least one flexion spring (14a, 14b, 14c, 14d, 14e) being configured and arranged so as to apply to at least one of the arms (10a, 10b, 10c, 10d, 10e), when the arms (10a, 10b, 10c, 10d, 10e) are released from the folded configuration, a thrust which causes the deployment of the arm (10a, 10b, 10c, 10d, 10e), characterised in that the flexion spring is generally biased in flexion when the arms (10a, 10b, 10c, 10d, 10e) are held in the folded configuration and generally works in flexion when the arms are released, at least one of the at least one flexion spring comprising an anchoring portion which is fixed relative to the reference axis r, and a deformable portion which becomes deformed when the flexion spring relaxes, the deformable portion being wound around the reference axis when the arms (10a, 10b, 10c, 10d, 10e) are held in the folded configuration and being unwound when the spring relaxes.