In the Time of Dinosaurs — K.A. Applegate

We could blame everything that happened on Marco. He was the one who heard about the downed submarine. He was the one who thought we should check it out. And everyone knows that if Marco's up to a challenge, I'm definitely there.Everything was going fine. Until the explosion. An explosion that blew us millions of years back in time, to the age of dinosaurs.Now Tobias, Cassie, Marco, Ax, Jake and I are fighting for our lives with every step we take. But that's not our biggest problem. Our biggest problem is we have no idea how to get back to our own time ...