The reason of that aspect of water is hidden in the different structure of the quarks composing the Oxygen and the Hydrogen nuclei.
A Hydrogen atom is made up of one positively charged proton whose charge is balanced by one negatively charged electron.
The Oxygen atom has eight protons (positive particle) and eight neutrons (neutral particles) in its nucleus. A nucleus surrounded by eight electrons. Because of the structure of Oxygen, they exist two open spots open in the electrons’ cloud. These spots are filled when a Hydrogen atom is in proximity of the Oxygen.
When Hydrogen bonds with Oxygen, the electrons that have bonded are formed into five pairs of ten electrons:
- one pair gives existence to the Oxygen atom's inner electron cloud;
- two pairs form the Oxygen atom's outer electron cloud;
- two remaining pairs form the O-H bonds, which create the polar molecule H2O.
Because of Hydrogen bonds, water has many of its known features.
Partial charges result in water molecules being strongly attracted to one another in the liquid phase. In other terms, for a group of water molecules, the positively charged H-atoms are electrically attracted to the negatively charged O-atoms.
One of the many features due to Hydrogen bonds is the familiar aspect for a drop of water. It derives by the H-bond extended to a macromolecular system with many participating molecules.
We can think of this attraction as water molecules tending to stick together, what in the video is clearly visible. This strong electrostatic attraction between Hydrogen atoms on one water molecule, to Oxygen atom on another, is called Hydrogen Bonding, or H-bonds.