Possible explanations for why those Cialis commercials feature a couple lounging outdoors in matching antique bathtubs:
Because he'd already bought one, the art director got a second antique bathtub for free.
The advertising industry ran out of ideas in 1987 so now they're just playing with our heads.
It's probably a euphemism for something. Or possibly a metaphor.
Whatever it means, it's still better than the ads with those guys sitting around singing Viva Viagra.