Is it normal to automatically know someone would be good in bed in fantasy

I had casually met this guy at the gym and fantasized about him just out of coincidence during masterbation. at the time I met him, he wasnt particularly attractive and I didnt think much of him. however, in my fantasy, his male organs suited my body perfectly. our movements together were heaven. it made me so hot that I want to bump into him again so hopefully he asks me out and I come to his house and maybe have some drinks and get him into bed. is THIS normal?