Sweat, Sweat, Baby! With the naked eye you can indeed see fingerprints, these shots here of Timelapse Vision but show really, as hilly but our adherence labyrinth. The close-ups give also in fast motion a very special view of the transcending salt water content.
There are a lot of tiny lines on fingertips and palm called epidermal ridges. The ducts of sweat glands is open on tops of the ridges causing prints that are left on a Surface.