The molecules in water stay very close together. This is because they are
attracted to each other. This attraction creates surface tension. Surface tension
holds water molecules together in drops when you try to separate them. It is so
strong that some bugs can sit on water!

Molecules at the surface only have molecules pulling them from below and on
the sides. This constant pull on surface molecules creates surface tension.

Water molecules are attracted to each other. The water molecules in the middle
of a drop of water are surrounded by others on all sides. The pulls on these
molecules cancel each other out.