Random story ideas with almost no plot & writing help

This is a book I was gonna write but then I realized I was in over my head

Doctor Chase preforms an autopsy on a man who seems to have somehow acquired some physical traits of a shark. Now the detectives think she, Annabeth Chase, a specialist in genetics, has helped mutate this man into something other. She now needs to find out who did this, how, and why, all while figuring out why her boyfriend is suddenly so distant.

Marine Biologist Percy Jackson has had trouble keeping his job. He worked as an aquarist as a side job to support his family. His girlfriend left him with two kids and barely any money, and though he enjoyed his side job, he just wished he didn't need it. He knew he needed this job, as much as he didn't want to believe it. Now he might be fired. First it was the eel. How was he supposed to know it was electric? And then was the crazy dolphin, Dave. Percy couldn't talk to dolphins! How was he supposed to know that Dave was hungry? But when he is offered a large sum of money by Dr A. Chase, he feels the need to help her figure out a mystery, all while grappling with his own rebellious feelings.

Join Percy and Annabeth on the mystery of the shark man, Charles Beckendorf and his creepy  girlfriend, Silena Beauregard. Can Percy and Annabeth navigate their feelings and keep their jobs all at once?

Find out in this thrilling tale of love, adventure, and mystery.