Danger, The (Dive: Book Three)

This highly recommended trilogy is about a dive internship that isn't, and a treasure hunt that isn't supposed to be, but is. The books focus on four young teenagers who are thrown together to supposedly participate in a summer research project, but find themselves thwarted at every turn. Finding support from other adults, the teens do get to spend considerable time in the water, and make an amazing discovery of two shipwrecks, including treasure.