Anyone who knows what the thing that this is a close-up of will have no trouble guessing what it is.
A lot of people will guess something similar but miss the mark just slightly, I bet.
Need a hint: I think not, today. See the full-size image below and an explanation…
It's the mouth of a Koi (Cyprinus carpio) that has come to the surface of a lily pond "in hopes of finding some food," say the photographers, Linda and Dr. Dick Buscher. "These native carp from Central Europe and Asia are now found around the world adding color and charm to man-made ponds. They were first bred for their color mutations in China over a thousand years ago."
In a nutshell, koi is domesticated, colorful carp.
Did you guess goldfish? That's what I would've thought it was, not knowing my Koi.