system
Given the following post, respond as if you're commenting on Reddit:
human
[Sharkboy & Lavagirl] How did Sharkboy's backstory of being raised by sharks also bestow his daughter with hyper hardened teeth?

None of his powers were genetic, he personally adapted to an aquatic environment and shark-like way of life.  How were his adaptations passed down?  Did he make her live underwater until she was shark-ey enough?
gpt
That's how Sharkboy himself got his powers. If you spend enough time swimming around the ocean, hanging with sharks, you develop gills, sharp teeth, and fins. 

No doubt he took her for long swims to visit his buddies in the sea when she was little.