The Shuigu is a special tool that resembles a golden cane with a ring at its end. When wielded, it can produce a limitless amount of water. If the wielder has control of the Shuigu, it creates water according to their will, such as rain that falls across a region or a constant stream flowing from its tip; the water can take shape if the wielder desires. If a wielder does not have control of the Shuigu, the water it produces is unchecked both in strength and volume, such that a simple desire to make rain will instead wash away crops and drown livestock. It is powered by the Sage of Six Paths' chakra and, according to Kakashi Hatake, draws its strength from the wielder. The nature of the strength it feeds off of is unclear as it is shown that the presence of desire alone can cast a powerful effect. The Shuigu itself is seemingly impervious to damage.
The Sage of Six Paths originally gave the Shuigu to the royal family of the Land of Redaku, an arid country that lacks enough water to sustain its people. In the centuries that followed, the country's monarchs used the Shuigu to provide for their people. Despite its importance to the country, its existence is not widely known of outside of the royal family, and those who do know of it avoid discussing it openly. But knowing about the Shuigu is not the same as knowing how to use it: when it passes to Manari from her father, there are no obvious reasons for why she's unable to control it. Some theorise that it can only be wielded by men, or that there's some special training she needs to undergo, or that there's a formal transfer of ownership that was not completed prior to her father's death.
In truth, wielding the Shuigu only requires that that a person sign its contract; the contract is stored within the Shuigu's staff, accessible by detaching the ring. Similar to a summoning contract, users sign their name in their own blood and mark the contract with their fingerprints. Nanara, after he signs its contract, describes having an inexplicable understanding of how to use it. He can feel something invisible flow from the Shuigu when in use, which he guesses to be chakra.