Adjustable swimming pool floor system, comprising: - a pool floor adjustable in a height direction relative to a pool bottom of a swimming pool: - a hydraulic system comprising: - a hydraulic cylinder, comprising a cylinder barrel having a cylinder head and a cylinder cap, a piston slideably arranged within the cylinder barrel and a piston rod carried by the piston, whereby a first part of the piston rod extends at an outside of the cylinder barrel beyond the cylinder head; characterised in that: - the pool floor is buoyant; - the hydraulic system further comprises a sealing arrangement slideably enclosing the first part of the piston rod remote from the cylinder head, whereby the sealing arrangement is connectable with an opening extending through a peripheral pool wall enclosing the swimming pool, from an exterior side to an interior side of the pool wall for extending the first part of the piston rod into an interior of the swimming pool adjacent the interior side of the pool wall, the sealing arrangement preventing leakage of liquid from the swimming pool to the exterior side of the pool wall; and the adjustable floor system further comprises: - a movement transfer arrangement connectable at a first end to the first part of the piston rod extendable into the interior of the swimming pool and at a second end to the buoyant pool floor, such that in use movement of the piston rod is transferred to the pool floor and adjustment of the pool floor in the height direction is achieved. - a pool floor adjustable in a height direction relative to a pool bottom of a swimming pool: - a hydraulic system comprising: - a hydraulic cylinder, comprising a cylinder barrel having a cylinder head and a cylinder cap, a piston slideably arranged within the cylinder barrel and a piston rod carried by the piston, whereby a first part of the piston rod extends at an outside of the cylinder barrel beyond the - the pool floor is buoyant; - the hydraulic system further comprises a sealing arrangement slideably enclosing the first part of the piston rod remote from the cylinder head, whereby the sealing arrangement is connectable with an opening extending through a peripheral pool wall enclosing the swimming pool, from an exterior side to an interior side of the pool wall for extending the first part of the piston rod into an interior of the swimming pool adjacent the interior side of the pool wall, the sealing arrangement preventing leakage of liquid from the swimming pool to the exterior side of the pool wall; and the adjustable floor system further comprises: - a movement transfer arrangement connectable at a first end to the first part of the piston rod extendable into the interior of the swimming pool and at a second end to the buoyant pool floor, such that in use movement of the piston rod is transferred to the pool floor and adjustment of the pool floor in the height direction is achieved. - a movement transfer arrangement connectable at a first end to the first part of the piston rod extendable into the interior of the swimming pool and at a second end to the buoyant pool floor, such that in use movement of the piston rod is transferred to the pool floor and adjustment of the pool floor in the height direction is achieved.