Ryouta Kajiki

An ocean-themed duelist appearing both in the Duelist Kingdom and Battle City arcs. Introduced in the Duelist Kingdom arc, he duels Yugi Mutou and is defeated. In Battle City he duels Katsuya Jounouchi, and his backstory is further expanded. It is revealed that Kajiki's father was a great fisherman that was lost at sea. In the English anime, Mako believes his father is alive and duels to raise money to fund a trip to search for him; in the Japanese anime, Kajiki duels in his father's memory. Jounouchi defeats Ryouta in their duel.

(Source: Wikipedia)