Curse of the Arctic Star (Nancy Drew Diaries) by Carolyn Keene

Nancy and her friends must navigate a cruise ship crisis in the first book of the Nancy Drew Diaries, a fresh approach to a classic series.

Nancy, Bess, and George are cruising dangerous waters on a tour of Alaska. Becca Wright, an old friend of Nancy’s, is the Assistant Cruise Director of the Arctic Star, a posh new ship. But Becca needs Nancy’s help when strange things keep happening aboard the opulent ocean liner: The swimming pool becomes a floating grave; a famous passenger is threatened; and even the seemingly innocent mini-golf course becomes a perilous playground. With the majestic and mysterious Alaskan scenery as a backdrop, Nancy and company have to find out who’s trying to sabotage the maiden voyage and why.