While Finnick is no stranger to being called beautiful, this is different. 'You're beautiful like this.' When he's losing himself to desire. Coming from someone else, it might make Finnick instinctually play up his moans and pleasured reactions, to put on a show for his partner. But coming from John, that urge isn't too strong. He somehow imagines that John would be able to tell if Finnick was faking it, even with how short a time they've known each other.

"Well, you have me now, sweetheart." He punctuates the sentiment by threading his fingers into the hair at John's nape and pulling at it very gently.

"Ahhh..." Finnick exhales a moan as he begins working him open in earnest, and his teeth bite harder into John's neck in response to the pleasure. Finnick is relaxed, and knows how to stay relaxed so that the process isn't uncomfortable. By now, he's so used to these feelings that he does unconsciously rush it a bit, pushing himself into John's fingers, arching his back even further.

Those words only further melt Finnick, making him feel drunk with desire.
"Fuck..." A curse hisses on the breath against John's neck. "That sounds amazing..." But right now, he wants to be fucked. He bites back his impatience, not wanting to rush John, letting him get his feel for things.

"More lube," is his main suggestion.