Kingfin is a giant skeletal shark shaped like a Fishbone. He has glowing yellow eyes that can emit a bright glow, improving his ability to see in the dark. He
To beat the boss, Mario must throw Koopa Shells at Kingfin's five times. After a single hit, Kingfin summons Fishbones that chase after Mario and explode on impact. These fishbones will immediately die outside his waters, as their bodies are held together by the water and collapse on land. Kingfin appears to be the ruler of the Fishbones.
- Kingfin is the only boss to be in a secret galaxy with only one mission.
- Kingfin's name is derived from Kingpin, a marvel comics super villain meaning big boss, and fin, coming from the fact that he was a fish.
- Kingfin makes an appearance in the Super Mario Manga Adventures. He appears in volume 40, having devoured the Mushroomers. The Mushroomers are freed from their prison, Toadette included, which Kingfin finds to his surprise.