The Old Man and the Sea is the 47th substory in Yakuza 6.
At the Jingai Ferry Dock, Kiryu enters an injured Isao. Isao explains to Kiryu that his injury will prevent him from being able to complete his fishing. He gives Kiryu the Standard Speargun and wants Kiryu to complete the fishing for him. Kiryu agrees to accept the offer and this serves as the tutorial for the spearfishing minigame.