This seems like a relationship pleaser to me. My girlfriend loves baths more than anything, but I like racing: cars, go karts, Hell even on foot. And we're always looking for something new to do together.
Two words: Bathtub Racer. We're talking fully motorized bathtub fun (No, not that kind of bathtub fun). For $17,000, you can get yourself 2 racers and an 65'x29' inflatable track. And we're not talking about a stupid little circuit track, this thing is a full on windy course.
Wait, did I just say $17,000? For a motorized Bathtubs and a track? Maybe I'll just wait for one to show up on Craigslist.
Product Page [Bathtub Racer via Random Good Stuff]