Two tone beach

The sun forgot to shine today, and the cloud barely lifted from the loch.
Result: a grey day with no horizon, a time with no time and no boundaries! The possibilities were endless!
The variations on this beach seem endless too. Today, it was 2 tone, half pebbles, the other sand. The daybefore, it was uniformly covered in pebbles. I don't think the waves are particularly strong, yet somehow the beach is rearranged daily.
How curious.