Boning In The Ocean: $290,000/Night Luxury Submarine
This is the Lover's Deep, a luxury submarine that rich people can rent to have sex in under the sea. It costs $145,000/night per person though and there's a two-night minimum, so unless you're planning on bringing a love doll for the least romantic getaway of all time, the minimum stay with another human being will set you back $580,000. I suggest going Dutch. The luxury sub comes with giant exterior-illuminated windows so you can watch all the fish and shipwrecks go by while you're boning. Just don't let your lover catch you eying the mermaids too hard mid-coitus, or you might have a problem. And do not, under any circumstances, call her Ariel. Just trust me on that one (I had a girlfriend break up with me for asking her to cinch her legs up in a trashbag and flop around in the bathtub).
Keep going for several more shots of the most magical two nights of your life.
Thanks to Dave, who claims he's had sex in Dr. No's underwater base from James Bond, and I have no reason not to believe him.