The descendants of WATANABE no Tsuna formed the 'Watanabe Party,' an armed group based in Watanabe no Tsu in Settsu Province, the seaport area at the mouth of the Kyu-Yodo-gawa River and were involved in the water transportation business in the Seto Inland Sea.
渡辺綱の後裔は、摂津国の渡辺津(大阪市中央区)という旧淀川河口辺の港湾地域を本拠地とする「渡辺党」と呼ばれる武士団を形成し、瀬戸内海の水運に関与した。