In Too Deep — Terri Alcock

Samantha Hope is a natural born snoop and budding writer of mystery novels. When her friend Bill Henry, a retired policeman, asks her to quit her job to go into the private investigations field with him, she jumps at the chance, not realizing just how easy it is for a novice to get into trouble.

As a favor to her neighbor's sister, she becomes embroiled in investigating the disappearance of a teenage girl. When the girl is later discovered drowned at Elk Lake, the police assume it is another case of a runaway suicide. But her grandmother refuses to believe that she could have killed herself and hires Sam to get to the bottom of it. With the help of her roommate Gabby and their two Old English sheepdogs, they try to discover who is responsible for the girl's death.