Debated. The sword may have been a warrior's, or a gift put in the water.
The sword was in the Warta River, near Wronki, in western Poland. From its shape, it is dated to the 11th century. The blade is about 76 centimetres long. The crossguard is about 12.5 centimetres wide. It was still in good shape after its years in the river.
The page still asks if someone lost it, or placed it in the river on purpose.
https://www.ancient-origins.net/news-history-archaeology/11th-century-sword-00102884