Perilous by Cari Z.

In 1803, England declares war on France, staking the fates of two mighty empires against one another. Thousands of men serve in the British navy, hungry for distinction in the battle against Bonaparte.

One of them, Lieutenant Thomas Williams, thinks he knows what he wants out of life: prize money at sea, a career of decent note, and the means to maintain his independence when he leaves the navy. What he finds is service under Captain Christopher Knightly: a tactical genius, inveterate charmer, and the youngest son of a wealthy noble house.
Their unexpected and perilous love affair is a gamble against the odds, for in a time of war, nothing is sure to last. If the French don’t tear them apart, one slip in front of the wrong eyes or ears might. When the demands of Christopher’s family take him from Thomas’s side, he thinks it might be the best thing for his captain. Little does Tom realize just how far Christopher will go to return to him, and when life takes a turn for the worse, how much further he will go to save him.