I reviewed the first one, Blood of Beasts, here.
Here is the Amazon blurb for Head under Water:
Titans are disappearing.
Holding facilities are being emptied of the government’s greatest asset. A single Titan is the only clue left behind.
Melody can’t speak. She can’t breathe air. She can’t leave the confines of her tank.
But she’s the only one who knows who is breaking Titans out of their cages.
Meanwhile, James is unable to accept his fate as a Titan. So much so that he is willing to make a deal with the devil to find the Antidote.
Can they turn back the clock, to when they were all human?
Geneshifters is perfect for science fantasy and dystopian lovers. Suitable for ages 12+, the series contains clean romance, no cursing, and some violence.