Group vs phase velocity

What you are seeing: a two-component superposition. The orange dot tracks the carrier crest (phase velocity); the cyan dot tracks the envelope maximum (group velocity). For light, $v_g = v_p$. For deep-water gravity waves, $v_g = v_p / 2$ (the envelope moves slower than the crests). For the Schrödinger free-particle dispersion, $v_g = 2 v_p$.