Old sci fi movie from 60's or 70's where spaceman or men come to earth and use disinigration gun. One scene where girl is in pool and is disinigrated to her skeleton. Actors mostly teenagers, young adults.

Laserblast.. maybe

Mars Attacks?

Possibly this one: Teenagers from Outer Space (1959) (http://www.imdb.com/title/tt0053337/)

Noooooooooooooo it's a frackin cartoon!

Ooops wrong post haha