What are the differences between a blue whale and a mega-mouth? Size and ... their skeletal structure, of course. A dolphin is extremely agile in water and is excellent at hunting for fish but it could not match the prowess of Great White in the open water. Intelligence can only get you so far because the Great White is many times larger than a dolphin but of lesser weight; the explanation lies in their cartilage which has advantages over bone.
I need my mermaid to escape from its jaws so which kind of backbone should my mermaid grow?