Piper Wayman is facing the most boring summer ever. Stuck in her artist dad's studio while he travels, her only excitement is complaining-until her long-lost grandmother Abby shows up. Abby isn't a cookie-baking grandma; she's a battle-hardened, retired sea captain with a duffel bag of mysteries and a weathered sailboat named Orcinus. Drafted as an unwilling first mate, Piper is thrust into a world of sextants, storm evasion, and a grumpy pelican named Mr. Flipflop. As Abby teaches her to navigate the unpredictable Gulf of Mexico, Piper realizes her grandmother is navigating a painful past, steering clear of the tiny island and the lighthouse where a childhood hurricane took everything. But the sea has its own plans, serving up flying fish, bioluminescent dolphin raves, and a pod of curious killer whales.