Agreed that the sea/sand confluence is very well done. But clearly the main sea mat is a commercial product witnessed by the imprint in the top left corner in the first photograph. Not sure if the beach mat is also commercial or an adaptation to match (there is a minor color variation between the two sea mats but that might be from age difference, batch difference, lighting, or close color matching or some combination of all of that).
What makes the confluence work so well is the sand is dry (lighter), damp (a little darker), and wet (darkest) as it goes from tree line to water line. And then that very nice set of surf lines with, maybe (could just be shadows) the color variation in the surf from white to a 'sandy' white which is very realistic since surf mixes with sand when crashing to shore.
So, yes, please let us know about either how it was done or source of mats if commercial.