The great whales
The verb bara, to create, is used a second time when animal life is bestowed upon creatures of the sea and air. The first mentioned is the תַּנִּין, tanniyn, an nonspecific designation for a fearsome creature sometimes called a "dragon". The creatures is said to be quite large. Their size alone would have demanded respect from all other animals in the sea. The contrast between the "monsters" and the "minnows", so to speak, is another merism.
The act of creating was universal in scope. Twice in this verse the Hebrew word כָּל, kal, is used. Be they in the water or the air, every animal was especially designed for its niche in God's world.