The blemington's have escaped!

Seen on the surface

Oddly reminescent of Superfast Jellyfish (All hail king Neptune).

Yet it does look like a Blemmington! Or maybe a cross between a Blemmington and a Zee Creature? A Zee Blemmington?

Indeed, I surmise that the blemington exscaped, crossed with something native to the surface, and then possibly passed away as light and jugement came to it. But the spawn seems to be hearty, and quite capable of surviving.