The Man Betrayed by the Sea Meitantei Conan : Season 1 Episode 750

The Detective Boys are invited on the yacht of a wealthy businessman in Shinta City. The owner's wife invited the group to eat on the boat. During lunch, the woman shows guys two videos: one in which the husband swims with the help of a tablet and one in which the man has finally learned to swim. After a few hours, the boys see the entrepreneur jump into the sea and drown.