Undercover Billionaire by Amy Andrews

Nobody can discover the truth about this sexy, forbidden fling.
Brooding billionaire Ari Callisthenes, heir to a Greek shipping line, goes undercover as a regular Joe passenger on one of his own cruise ships to find out why it’s underperforming. His standards are impossibly high and he isn’t willing to leave anything to chance but unexpected chemistry with a sexy cocktail waitress has him reassessing his priorities. And his rules.

Australian Kelsey Armitage lets her guard down for the first time in a long time. Romance with the mysterious passenger is strictly forbidden but for once Kelsey is prepared to break all the rules….and have a lot of fun doing it.
Ari’s subterfuge puts everything that Kelsey has worked for at risk. Can she ever forgive the tycoon for his deception?