Jinbei is a whale shark fishman who serves as the helmsman of the Straw Hat Pirates. He is a massive individual with light blue skin, a stocky build reminiscent of a sumo wrestler, and facial features that draw from Japanese folklore, particularly the demonic oni, including yellow eyebrows and sideburns shaped in a distinct pattern along with two large tusks protruding from his lower jaw. A lightning-shaped scar runs from his left sideburn down over his left eye. He typically wears traditional Japanese garments, often a kimono of various patterns paired with a coat, and wooden geta sandals on his webbed feet.

In terms of background, Jinbei was a soldier in the Neptune Army of the Ryugu Kingdom before becoming a pirate. He joined the Sun Pirates under the leadership of the legendary Fisher Tiger, serving as Tiger's right-hand man. After Fisher Tiger was fatally wounded and died, Jinbei took command of the crew, becoming its second captain. Years prior to the main events of the story, he accepted an offer to become one of the Seven Warlords of the Sea, believing that this position would help protect Fishman Island from external threats. Ultimately, he renounced this title during the Battle of Marineford, refusing to fight against the Whitebeard Pirates, to whom he felt deeply indebted.

Jinbei's personality is defined by a profound sense of pride, honor, and duty. He is a thoughtful and intelligent individual who carries a heavy sense of responsibility, particularly for the safety of his homeland, Fishman Island, and his former crewmates. Unlike former crewmate Arlong, who harbored a deep hatred for humanity, Jinbei is capable of treating humans with respect and acknowledging debts owed to them. While he possesses great emotional control, he is also empathetic and has been shown to weep openly when losing someone dear to him, such as Fisher Tiger or Portgas D. Ace. He is known to put his principles over his personal honor and is not above retreating from a fight if it serves the greater good. His ultimate dream, as stated by a friend, is to see the establishment of true friendship between humans and fishmen.

His primary motivations stem from a desire to protect his people and honor his obligations. He holds Edward Newgate, Whitebeard, in the highest regard because the emperor claimed Fishman Island as his territory, thereby ending the rampant kidnapping and enslavement of its inhabitants by pirates. This debt of gratitude is the reason Jinbe refused to fight against Whitebeard in the Paramount War, even at the cost of his Warlord title and his freedom. His friendship with Ace, forged through a five-day-long battle after Ace attempted to kill Whitebeard, also drives him to aid Luffy in rescuing his brother.

Jinbe's role in the story evolves from a powerful ally to a core member of the Straw Hat Pirates. He first formally meets Monkey D. Luffy while imprisoned together in Impel Down. During the ensuing war at Marineford, he becomes one of Luffy's most crucial protectors, saving his life multiple times and helping him cope with the traumatic loss of Ace. After the war, Luffy formally invites Jinbe to join his crew. Although Jinbe declines at that time due to unfinished business with the Emperor Big Mom, to whom he had sworn allegiance to protect Fishman Island, he makes a solemn promise to join in the future. He finally fulfills this promise during the Whole Cake Island arc, officially becoming the Straw Hats' helmsman, a role in which his immense strength and expert ship-handling skills prove invaluable.

Key relationships define much of his journey. His captain, Monkey D. Luffy, is someone he respects deeply, and he is fiercely loyal to him as a subordinate. He felt tremendous guilt for allowing Arlong to travel to the East Blue, an act that led to great suffering for Nami and her village. He shares a deep bond with his former Sun Pirates crewmates, including Aladine, to whom he eventually entrusts the captaincy. He also maintains a strong friendship with the octopus fishman Hatchan.

Jinbei has shown considerable development, transitioning from a more brutal and aggressive warrior in his youth to a calm, wise, and principled leader. While he once shared the common fishman distrust of humans, his experiences with figures like Whitebeard and Luffy have broadened his perspective, allowing him to become a bridge between their two worlds. He also evolves from a captain responsible for his own crew to a trusted and integral member of another captain's crew.

Regarding notable abilities, Jinbei is an exceptionally powerful fighter and is considered the series' most skilled practitioner of Fish-Man Karate. This martial art is devastating on land but reaches its full potential in the water, where a fishman can use their immense strength to manipulate the water itself. His techniques include Water Shot, where he flicks a droplet of water with the force of a cannonball, and Vagabond Drill, a powerful piercing attack. He is also proficient in Fish-Man Jujutsu, an underwater style that allows him to grip and redirect ocean currents as if they were solid matter, as seen with his Ocean Current Shoulder Throw. His physical strength is immense; he was able to fight Portgas D. Ace to a standstill for five days and has survived direct, powerful blows from Admiral Akainu. As a fishman, his physical strength is naturally twice that of a base human on land and ten times that in the water, and he is an incredibly swift and powerful swimmer. His bounty has increased significantly over time, reflecting his growing infamy and strength, from an initial 76,000,000 berries to over one billion berries as a member of the Straw Hat Pirates.