Is it science or is it magic? It is probably both and this makes experiments like the floating paper clips so fascinating and fun to implement in the science classroom. You can try it yourself and have your students debate about the experiment. With a little caution they can even make paper clips float on the water themselves.
Water molecules have a greater attraction to each other than to the air molecules at the surface. In the middle of the waterglass, the attracting forces act from all directions. However, the molecules of the water surface are pulled only from below and the side, so that the uppermost layer of water has a special stability and is like a skin on the water. A paper clip with its whole area spread out on that layer of water does not break the stability and therefore floats.
Fun fact: a drop of dish soap destroys the surface tension and the paper clips sink to the ground. You can try it at home!