Doomed Seas. Black Depths, #4

A fast paced young adult adventure that will captivate the hearts of pirate lovers. Caesar knows he's running out of time to find his father, who's been missing for over a year. When he discovers his own grandfather, Victor, is behind not only his father's kidnapping, but the kidnapping of innocent Neptunians all over the globe, Caesar sets sail to find what Victor wants most. In the company of his best friend Markus, and ex-girlfriend Darya, the pirates begin their journey across the seas.
But things aren't always as they seem. The more Caesar discovers, the more he questions his loyalty. Then Caesar is given an important clue to the location of the treasure Victor hunts. Can he untangle the strings of desire, history, and hope in time to find the treasure, or will this hunt be his last?