Because Metal fears being buried by Earth and also fears being submerged by Water. Too much Earth buries Metal, keeping it from the light of day, and too much Water submerges Metal, which also keeps it from the light of day. A sword submerged in water is called "broken weapons sinking into the sand," where "sand" refers to the silt at the bottom of a river. The famous Tang Dynasty poet Du Mu wrote a well-known poem while visiting Red Cliff: "Broken weapons sink into the sand, their iron not yet rusted; I take them to polish and recognize the former dynasty." If the east wind had not favored Zhou Lang, the bronze crows would have locked the two Qiaos in the springtime of the Cuque Pavilion.
At that time, a weapon from over 600 years ago was recovered from the riverbed, covered in rust, and the poet was moved to write this famous line. However, weapons submerged in the riverbed have no practical value in battle, but if they were passed down to modern times, they would have some aesthetic value. As for jewelry submerged in water, there's no need to say more, like the story of Du Shiniang angrily sinking her hundred treasures box—no matter how many treasures, they lose their exchange value.

Year of Bing Zi: Water of Stream (1936, 1996) Year of Ding Chou: Water of Stream (1937, 1997)
Year of Jia Shen: Water of Spring (1944, 2004) Year of Yi You: Water of Spring (1945, 2005)
Year of Ren Chen: Flowing Water (1952, 2012) Year of Gui Si: Flowing Water (1953, 2013)
Year of Bing Wu: Heaven's Water (1966, 2026) Year of Ding Wei: Heaven's Water (1967, 2027)
Year of Ren Xu: Sea Water (1982, 2042) Year of Gui Hai: Sea Water (1983, 2043)