The 2.4GHz radiation behavesMORE like visible light, so we have to think of reflections and shadows.
Flying a 2.4GHz radio control model over a reflective surface like water, snow, ice or wet terrain
negatively affects the radio link. OCCASIONALLYa 3D aerobatic model plunges into water while hovering.
When the rudder is near the water surface, the prop wash creates a chaotic wave pattern which generates
a myriad of false-signals.

The reason why microwave oven operates on 2.4GHz is that this frequency excite the water molecules best.
Since the human body contain plenty of water, it is possible that the person between the pilot and the model
may cause interference as SPORT PILOT described.