遡 means 'go upstream'

A waterway poses challenges to travelers, but such obstacles are surmountable, as all these kanji demonstrate. Both 越 and 渡involve crossing rivers via bridges or boats, and 越 is in a town name that actually means "crossing the river." As 沖 often pertains to fishing some distance from the shore, crossing that water reaps benefits. With 遡 one goes upstream, either along the shore on foot or in the river itself if one is a salmon looking to spawn. The carp, which famously swims upstream, symbolizes courage, spirit, and achievement for conquering the challenges of a waterway.