Kate B. Jerome has a series dealing with the OceanX expeditions, and book two is Danger in the Deep Sea (2) (OceanX Adventures). As an 8 to (young-medium) 12-year-old I would have devoured this book/series. I did not realize this was book two when I “picked up” the online reader copy. And while it can be a stand-alone read, it probably would have helped to read book one first. The adventures of the story are unbelievable, yet, probably plausible. Our main character is a treasure hunting crazy twelve-year-old girl. And when she accidently stows away on the OceanX ship her brother has gotten a summer internship on, she starts her journey to true treasure.
The theme is that Spoiler: the most precious treasure is her brother/family and friends, instead of real treasure (and though I get that, I still was peeved when something happens to the potential treasure chest). Things are a little sappy, but kid me would not have cared. It is a good adventure story where things get “tense” but everything is “clean” and “safe” and you know things will work out okay.
This book is a promotion for the real OceanX team and while there is nothing wrong with that (in fact I enjoyed the afterwards that gives more information about things we saw and the real people behind it), just know there is a plan they promote. Overall, a fun and cozy book.
I will be (or hopefully will) be reading book one soon. At least Mystery at the Aquarium (Oceanx Adventures #1) is on my TBR list of online reader copies (as two was read) though both are currently available. 
