Known for not bothering with/knowing how to use the
Type Chart.
Dark/Fire is indeed weak to Water-type moves, as well as Fighting, Ground, and Rock. No double weaknesses, though.
It's resistant to Ghost, Steel, Fire, Grass, and Ice, as well as completely immune to Psychic.
Interestingly, in the Pokemon world, Dark/Steel exists, but isn't indestructible at all. It's immune to Poison and Psychic, as well as resistant to many types (because Steel), but weak to Ground and Fire and doubly weak to Fighting.