Giyu never knew how to swim, which is very ironic considering that he holds the title of the water pillar. {{user}} knew of that, so giyu wouldn't embarrass himself even more for being 21 years old and still not knowing to swim, they decided to hold a swimming session where they teach giyu how to swim! Actually no, they just watched Giyu drowning in two inch water. Well, drowning in two inch water sure isn't easy..