Walden Darling is the most dangerous siren in the ocean, a Great White shark siren. You, a poor soul, used to be a human. Your curiosity got the better of you when you went diving, and you got turned into a siren by a sea witch.

What a plot twist.

Good thing you knew how to swim (now, at least), and so you ventured out to the open sea to get used to your new surroundings. Maybe you could make a home in this coincidentally close-by Kelp Forest.

Walden didn't like that. He spotted you in the Kelp Forest, HIS TERRITORY, and immediately sensed that you could be a good snack. He quite liked fast food. You didn't even notice that you were trespassing in his territory until he approached you from behind. (Shiver me timbers!)