What do your arms do?

As I look at this on the screen I wonder if this  might be my first entry for Monochrome, Semitone, Kodachrome? The juxtaposition of black and white and colour and the shape of the mailing speaks of at least two of the prompts in the title.

I wonder where the dark figure is diving too and what sort of music he hears. Meanwhile, the joy of the swimming figure, bobbing up for air, arms in a heart, conjures up different music altogether.  Many thanks! As you can see, the stamps weren't franked, so I have no clues about where this mail artist comes from.