How do they shoot the music videos where people are singing inside water? What confuses me if that is plain special effects is their clothes, they behave exactly how clothes behave in water.
The motion of the cloth is slow, like it's supposed to be in a fluid, whereas the motion of the person is normal (or slow, but for stylistic reasons). I mean, it could be special effects, but that will really surprise me, because it will certainly take a lot of effort.
Example: