Stephanie Lacsa told San Diego County authorities she noticed the water level in the toilet was higher than usual when she went to the second-floor restroom Tuesday. When she plunged it, a snake popped up and flicked its tongue.
She ran out, taped the door shut and called Animal Services.
The department says an animal control officer found a giant Columbian rainbow boa on the floor. The snake was shedding and slightly underweight.
It was taken to an animal care facility and bit a handler.
If the owner doesn't show up by Friday, the snake will go to a rescue group.
How it got in the toilet remains a mystery.