It's been a while since I've taken Chemistry but here's what I know:
There are small, weak bonds that form between water molecules. These bonds make it so liquid molecules (water, in this example) cannot move as freely as a gas, but their bonds aren't nearly as strong as a solid. The bonds are formed when a hydrogen atom is attracted to an oxygen atom (because they have an opposite charge). This bond plus the gas molecules hitting the water causes surface tension.
(Let me know if this is wrong and I hope you have a lovely day!!)
