Based on the new mob that was originally made for Minecraft Earth, wich is a squid, but with an animated and luminescent texture. It looks a bit derpy but i hope you like it. I used gootube2000's amazing mini squid design as a template to make this one, it's the same thing, just retextured :P

Source: https://minecraft.gamepedia.com/Minecraft_Earth:Glow_Squid