The line tender / by Kate Allen.

Enhanced descriptions from Syndetics:

Wherever the sharks led, Lucy Everhart's marine-biologist mother was sure to follow. In fact, she was on a boat far off the coast of Massachusetts, collecting shark data when she died suddenly. Lucy was seven. Since then Lucy and her father have kept their heads above water-thanks in large part to a few close friends and neighbors. But June of her twelfth summer brings more than the end of school and a heat wave to sleepy Rockport. On one steamy day, the tide brings a great white-and then another tragedy, cutting short a friendship everyone insists was 'meaningful' but no one can tell Lucy what it all meant. To survive the fresh wave of grief, Lucy must grab the line that connects her depressed father, a stubborn fisherman, and a curious old widower to her mother's unfinished research on the Great White's return to Cape Cod. If Lucy can find a way to help this unlikely quartet follow the sharks her mother loved, she'll finally be able to look beyond what she's lost and toward what's left to be discovered.

Funny, poignant, and deeply moving, The Line Tender is a story of nature's enduring mystery and the people willing to seek meaning and connection within it.