The Water 7 Saga is one of the biggest storytelling arcs in the manga and anime series One Piece by Eiichiro Oda. This saga includes two major arcs: the Water 7 Arc and the Enies Lobby Arc. In the anime, it corresponds to season 8, directed by Kōnosuke Uda and Munehisa Sakai. The saga is interesting because of its complex plot and character development, showing a number of changes in the crew dynamics of the Straw Hat Pirates.
The Water 7 Arc, also known as the Capital of Water Arc, is the fifteenth story arc in the series. The city introduced in the arc is Water 7, similar to Venice, famed for its shipwrights and being the main headquarters of the Galley-La Company. This arc starts with the Straw Hats seeking to repair their ship, the Going Merry, and recruit a shipwright into their crew.
Key characters that are introduced during this arc include Franky, a cyborg shipwright who becomes part of the Straw Hats later in the series, and members of Galley-La Company: Iceburg, Paulie, Lucci, Kaku, and Kalifa. These characters play a rather central role in the drama unfolding, very central to most of the plot twists within this arc.
One of the most overwhelming events of the Water 7 Arc was realizing that there was no way Going Merry could be revived. This made the crew emotional, but much more so for Usopp, who thought it was a gift from his late friend Kaya. This conflict over what to do with the Going Merry resulted in a battle between Luffy and Usopp, one of the most emotionally charged moments in the series.
The Water 7 Arc is also where the CP9 was introduced—a secret organization working for the World Government. Most of its members are Rob Lucci, Kaku, Kalifa, and Blueno. At first, they worked for Galley-La as cover for their espionage subplot in this arc. Their turning into antagonists is one of the major plot twists in this saga.
One of the elements that makes Water 7 so unique is its annual Aqua Laguna, a huge tidal wave that swamps lower parts of the city. This element he has added to his created world helps to heighten tension in the events of the arc and shows how Oda really pays attention to the details of the world he is building.
Well, the saga spills over into the Enies Lobby Arc as well, where actually, the Straw Hats follow CP9 to rescue their crewmate, Nico Robin. So, Enies Lobby— Judicial Island, as many may know it—became a government stronghold and an intense battleground between the Straw Hats and CP9 agents for rescuing Nico Robin.
The Enies Lobby Arc introduces several new abilities and power-ups for the characters. Luffy reveals his Gear Second and Gear Third techniques, which boost his fighting ability greatly. Other members of his crew are also given new moves like Zoro's Asura technique and Sanji's Diable Jambe.
What is unique about this Water 7 saga is the underlying themes it brings forth into this world of One Piece: absolute justice, practiced by the World Government, compared to the justice being pursued by the Straw Hats. Furthermore, it draws on loyalty and friendship for one's friends, enough to fight for the sake of companions against higher powers.
One of the most memorable sequences in the saga is when the Straw Hats declare war on the World Government by burning their flag at Enies Lobby. It would be a symbolic act against the oppressing authority, proclaiming that they were major threats against them.
It will bring about some major developments in the Straw Hat Pirates toward the end of the Water 7 Saga. Franky becomes their shipwright, and they get a new ship, the Thousand Sunny, to replace the Going Merry. The saga concludes with the sad goodbye to the Going Merry in a Viking funeral, a scene said to be one of the most touching moments in the series.