Dive

Dive is a series by Gordon Korman, the author of Everest and Island.   

Usually, Korman's books usually have a group of four main characters, all of which are kids. Usually, one dies at the end of the third book, which is impossible to tell from now, but this book has an interesting quirk. It keeps the same narrator the whole time, but it keeps switching between two settings (one of them would make a great example in social studies). One of the settings is in 1666, while the other is in the present. I am not sure of this, but I think the kids in the present are searching for the setting in the past because at the very beginning, the 1666 setting crashed to the bottom of the ocean. My evidence comes from page 80, when of the kids found a piece of eight and they thought it was a chipped-off part of an anchor. 

This book's a mystery about why they were assigned to dive. Who knows what will happen in book 2?