Medusa — Skye Kathleen Moody

Strange things are happening in Washington State's beautiful Elliott Bay, but U.S. Fish and Wildlife's star agent Venus Diamond is on medical leave after being shot in the line of duty. At least she is until her family needs her help: A bratty young girl, Pearl Pederson, goes overboard and drowns while yachting with her brother, Henry, and their well-to-do next-door neighbor, Tim Diamond. Tim claims he saw a huge, tentacled arm come out of the water to sweep the child to her doom, but Henry swears Tim pushed her, so twelve-year-old Tim is charged with murder. Venus knows her brother is innocent, but also knows she'll have a devil of a time proving it.
Days pass, and speculation abounds until Pearl's body washes ashore, full of puncture wounds and looking very much like the victim of some strange sea creature. It's just the first in a string of similar events, and before long the whole city of Seattle is abuzz with the possibility of a sea monster in Elliott Bay.
Venus Diamond knows there must be a more logical explanation for the killings, however, and sets out to find out what's happening, including looking into some strange goings-on at the Elliott Bay Marina. She'll need all her environmental expertise to find the elusive connections.