How can I get the rupees from the fishhead-like entrance eyes in Floria waterfall?

Replaying the game in hard mode, and I'm trying to be very thorough and discover things I missed the first time. I've got all dowsing abilities enabled, and I'm dowsing for rupees and treasure, mostly to discover breakable walls or hidden stuff I missed. This way, I discovered that there are flags in Skyloft that can produce rupees using the gust bellows, fires in alcoves produce rupees if blown upon too, lanterns produce rupees if hit with deku seeds etc.

At the Floria waterfall, the large fishhead-like entrance has two large eyes that seem to be active when dowsing for rupees, but I can't get these rupees. I've tried the clawshots from the closest lilly (too far), arrows, beetle to no avail.

Does anyone know how to get the rupees from the eyes of the fishhead entrance;

The beetle is what I used. If its fully upgraded it works a lot better.