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I try to stand on water surface but I just drown. A book resting on the table because of the W(gravitational Force) and normal force of the table acting on the book oppositely in equal magnitude being canceled out. When it comes to a fluid (air, water, oil etc) If I put my two feet on the surface I will simply drown. Why that? See, the weight of my body is acting on the surface and according to the third law at that instant there will be an equal and opposite force acting on me from the surface. So should not I be able to stand? If you are about to say that fluid molecules have surface tension and they are not steady then I would like to say the little portion of weight of any point of my body that pushes the tiny fluid molecule, that tiny part should cancel that little amount of weight. By this each and every point of my body (along with my Centre of gravity) part should have a net 0 force which should make stand on the fluid surface theoretically. But in practical case it doesn't happen. Why that? I can stand on frozen Lake but can't stand when it is not frozen.