Murder Walks the Plank (Death on Demand Series #15) Book

I enjoy this series, but the plots are getting a little far fetched. In this book, a woman falls off the deck of a Mystery cruise sponsored by Death on Demand bookstore. She is a woman with no enemies, and even though it is discovered that she was probably unconcious when she went flying over the rails, the police consider it accidental. Another murder then keeps Annie busy trying to discover the murderer on the island. The next to last chapter has the brief scary encounter with the murderer trying to execute one more murder with a family member in danger.