Glow squid suffocates in water

While digging an underground base in my Survival world, I built a 3x9x1 "pond," with a 2x1x2 hole in the leftmost corner for axolotls to spawn in. Instead, a single glow squid eventually spawned. It swam around for approximately 1 minute while I watched it, before inexplicable starting to take damage in the center of said pond.

I do not know how to reproduce the results, as it took several hours for the glow squid to spawn naturally