Steve Brezenoff 
Unsinkable Ship [PDF ebook] 

After Tucker and Maya are jolted back to the present by Titanic’s iceberg collision, they don’t know what will happen to their new friend, Liam, who is still trapped onboard. They travel back to 1912 again to make sure Liam and his parents, all third-class passengers, make it to the lifeboats in time. But none of the passengers seem to realize the severity of the situation. Tucker and Maya must convince everyone that the unsinkable ship is sinking, and find Liam, before it’s too late.