His Need, Her Desire (Dominating BDSM Billionaires #1‪)‬

Executive assistant Tabitha Quinn didn't come to Hawaii to be spanked. But when vacationing businessman Marcus Granger saves her from drowning, they begin an affair that moves from the beach to the bedroom and straight into an experience Tabitha's never had before: dark-haired, blue-eyed Marcus is a dominant, and spanking is just the beginning. The sex is intense, the emotion even more so, until they both must decide if this is a holiday fling or the real thing.