Death at Lavender Bay — Lauren Wright Douglas

When Allison O'Neil is called for the reading of a relative's will, she is astonished to find herself an heiress. It seems her Aunt Grace … from whom she received little more than birthday and Christmas cards … has left Allison a bed-and-breakfast in the tiny town of Lavner Bay, Oregon.
From the moment she arrives to claim her legacy, however, Allison is haunted by an uneasy feeling that things aren't quite what they seem. Although the locals express deep fondness for Aunt Grace, no one will discuss the circumstances of her death. And the odd assortment of people who live at the bed-and-breakfast are not paying guest, they're permanent residents … each of whom has benefited financially from Aunt Grace's untimely demise…
Allison's worst fears are realized when she discovers that Aunt Grace allegedly drowned while snorkeling … an unlikely pursuit for a woman who couldn't swim and was terrified of the water!