NOVELTY - The apparatus has a buoyant member (305) with a through hole (350) through which a post (340) extends. A pump unit (310) is driven by rise and/or fall of the member with rise and/or fall of a level of a fluid such as a level of tide or varying water level from a flowing river. A guide unit (341) is provided around a circumference of the hole so as to accommodate lateral movements between the member and the post. The guide unit includes a set of rolling dampers circumferentially disposed around the hole, where each rolling damper includes a roller or wheel and a shock absorbing member.    USE - Power generator apparatus such as electrical power generation apparatus and water purification apparatus and/or desalination apparatus e.g. reverse osmosis (RO) desalination apparatus, for water purification and/or desalination and/or power generation using a structure e.g. building with enclosed space such as domestic space, educational/institutional space, commercial/industrial space and office space, room such as hotel room, meeting room and dining room, that is utilized for sports playing area such as tennis court and golf court, and for horticulture and agriculture (claimed).    ADVANTAGE - The apparatus provides renewable energy sources e.g. wind, and supplies fresh water, while harnessing power in the rise and fall of the tide, and functions in sheltered coastal locations.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are also included for the following:    (1) a structure comprising a buoyant member    (2) a pump device comprising a buoyant member    (3) a water purification and/or desalination apparatus comprising a buoyant or floating structure    (4) a method of water purification using a buoyant or floating structure    (5) a method of power generation    (6) a building structure comprising a buoyant member    (7) a buoyant member having a landscaped and/or grassed area    (8) a power generation apparatus comprising a buoyant member.    DESCRIPTION OF DRAWING(S) - The drawing shows a side view of a buoyant structure.    Buoyant structure (300)    Buoyant member (305)    Pump unit (310)    Piston (325)    Piston rod (327)    Knuckle (328b)    Gantry (329)    Post (340)    Guide unit (341)    Through hole (350)