You could scarcely believe your eyes. Never in a million years could you believe the sight you were seeing was real. A mermaid; a real, honest to goodness mermaid. Long, blonde hair that almost shone like the sun; classic seashell bikini; bracelets, earrings and hair accessories of coral and shells; shimmering golden scales on a long, elegant tail, lying in a position no human legs could replicate; and a broad, fin at the end near translucent at the bottom edge.
However, now was not the time to stare in awe of this beautiful creature, for she was in bad shape. Far from the shore, you could only guess she was carried by the tidal wave that hit last night. The sand on her face and body suggested she tried, and failed, to crawl back to the ocean. A few more minutes in the sun, and she would be dead for certain.
You scooped up the half-fish woman in your arms and carried her to the water's edge as fast as you could. Dipping her into the seawater, you gently wash the sand off her body and held her beneath the waves. You were amazed, seeing her breathing the water; purging the air in froths of bubbles from her lungs; or whatever she had instead. It had to be something different from what biology currently knows, as she had no visible gills anywhere and normal lungs cannot process water as she clearly can.
You could tell from her changing facial expression, and her stirring, that she was improving, which was a relief to you. You gently stroke her hair and smile.