I knew a girl in high school who claimed she was born with gills. She did smell kinda fishy.
In the womb, for a short time, we all have gills.
She probably just had some sort of branchial fistulas or sinuses, and wanted to make the condition sound cool.
Oh, I know her. Met her in college
She had these little flaps in her neck and they looked like they might have cartilage in them. It was pretty weird looking.
To this day I can't figure that one out. I only hope she found a plastic surgeon.