I can just imagine Kisumi's tail stalking across the water like a fin as she closes on Momiji's rear.

i think your a bit off, kisumi is not here, its momiji and tenshi

Read the comment again, it was a "what if" about me closing in on Momiji's ass. But you see, Momiji's blush and lowered ears, as well as support on the rocks, is because I'm under the water licking her love hole. This also explains the direction of Tenshi's "wtf" look, and why her back end is supported even though the water is clearly deeper.