The answer is: Whale

Gen 1:21 - The NIV renders this as 'great sea creatures'.

In the creation story, specifically in Genesis 1:21, the "great sea creatures" are often understood to refer to whales, which captivates our imagination because these majestic beings are like the ocean’s gentle giants. It's fascinating to think about what this means in terms of God's creative activity. The Bible emphasizes God's ability to bring forth a diverse array of marine life, which not only reflects the complexity of creation but also paints a vivid picture of the deep life forms that flourish in the vast oceans.

Here’s a fun tidbit: the Hebrew word for “great sea creatures” is *tanin*, a term that can broadly refer to any large aquatic entity, from mighty serpents to leviathan-like creatures. This opens up the possibility that the passage is pointing to something truly awe-inspiring and mysterious, perhaps even to thought of as spiritual symbols of chaos subdued through creation.

In addition, Jewish tradition and various ancient Near Eastern myths often had their own imagery about sea monsters, hinting at a cultural dialogue around these deep-sea existences. It underscores a burgeoning appreciation for biodiversity and invites us to reflect on our relationship with nature—an idea that reverberates through modern eco-theology. The detail of these creatures being created first in the underwater world helps symbolize life both great and small, emphasizing every living being’s value in the tapestry of creation.