Here's the design of Skar, Aqua's uncle and Ryujin's brother.

As you can see, Skar, a great white shark merman, is the primary antagonist in this series.

Just like Scar from The Lion King (both 1994 and 2019), as the younger brother of Ryujin and second-born Prince of the Atlantis, Skar was next in line to assume the throne as king.

However, his line of succession was replaced upon the birth of his nephew, Aqua. This embittered Skar with jealousy and a sense of entitlement, prompting him to develop a regicidal plot to take over the kingdom, with the aid of his pirate crew... And the titans.

I hope you like this design of Skar.