Gintama Episode 19: Why`s the Sea So Salty? Because You City Folk Pee Whenever You Go Swimming!
Episode 19 of 201 of Gintama, aired August 7, 2006, 25 minutes. Available with English subtitles and dub where released.
Episode summary
In an effort to get some quick cash, Gintoki and Hasegawa, along with Shinpachi, Kagura, and Otae, head to the beach to get rid of a monster that's been terrorizing the area.