Freshly certified as a young diver, 12-year-old Fernando "Fin" Román loves to spend his days at sea around the Florida Keys alongside his strong Abuelo Kiki in search of legendary lost treasure. The treasure hunt, moreover, marks a thread through Fin's Cuban and Puerto Rican family heritage, starting with his great-grandfather. Misfortune strikes one day while Fin and Abuelo are at sea, and Abuelo has a stroke, requiring Fin to radio for help and pilot the boat back to the marina. With Abuelo in the hospital, Fin hatches a plan to find the treasure on his behalf, reminding himself: "Plot my coordinates. Chart my destiny. Save Abuelo. Find the family legacy." To do so, he needs to enlist the help of his father, whose safety-conscious attitude annoys and repels adventure-loving Fin. There's another catch: Certified adult guides must accompany Fin on his dives, meddling in (and perhaps threatening) his hunt. As Dad gets fed up with the hunt, time runs out for Fin even as Abuelo's health seems to fade. Fin and his dad must rely on and trust each other to overcome obstacles--seen and unseen--in search of the treasure. Rodriguez packs a ton of local historical know-how and genuine humor into a seaworthy debut adventure. Lighthearted yet solid prose and quirky, delightful characters round out this swell tale of plucky fun under (and above) the sea. Here be treasure indeed. (author's note) (Fiction. 8-12) Copyright (c) Kirkus Reviews, used with permission.