The First Mate has brown skin, light brown eyes and short, chocolate brown hair parted on the left. The ship uniform consists of three-quarter length blue sailor pants with gold buttons at the pockets, a blue and white striped T-shirt, orange neck scarf, brown knee-high boots and brown gloves. In addition to the uniform, they also wear gold stud earrings.
In their first appearance, the First Mate is shown to be worried over fighting a Sea Feilong, claiming to have never fought a Grimm that size before. They are shown to be competent under stress. After Yang's trip aboard the ship, the First Mate is shown to be friendly to the passengers.
- Kai Ziegler, the First Mate's English voice actor has stated that their headcanon for the first mate is the name Matte Skye and that the first mate is nonbinary. Ziegler also consistently uses the pronoun 'they' when talking about the character. However, this has yet to be publicly confirmed by Rooster Teeth.
- Matte is a German name meaning "meadow", bringing greens to mind. Skye is derived from sky blue.