Proto-Indo-European *sel-es- "swamp, marsh, sea" became Indo-Iranian *saras- "body of water", then *saras-vatī "of waters" (*vatī meaning "containing"), then Sanskrit सरस्वती Sarasvatī, the name of a sacred river and the Hindu goddess.
*sel-es- became Greek ἕλος (helos) "marsh" then ἑλώδης (helōdēs) "marshy". This was borrowed into scientific Latin as Elōdea, a kind of aquatic plant. The American Heritage Dictionary of Indo-European Roots misspells this as eloidea, I think. At least, eloidea doesn't mean anything that I can determine.