In Roblox's Fisch, Calm Zone is the fourth of the Mariana's Veil sub-locations, which fortunately does not contain any danger, so you can really just relax, rest, and fish.

In Roblox’s Fisch, Calm Zone is the fourth area in Mariana’s Veil, and it’s a safe haven where you can unwind, relax, and enjoy fishing. This location boasts a variety of nine fish species that you ...

By referring to the above table, you should easily be able to catch all the fish in the Calm Zone. As soon as you complete the bestiary, you will get the "Bestiary ; Calm Zone" badge, XP, and ...