IPA: /ˈsiːˌwɔːtə/
KK: /ˈsiːˌwɔːtər/
The salty water found in the sea or ocean.
The seawater was too salty for drinking.
Seawater is formed from "sea" (from Old English *sǣ*, meaning a large body of saltwater) and "water" (from Old English *wæter*, meaning liquid that falls as rain or is found in rivers and lakes). The word "seawater" refers to the water found in the sea, which is typically salty.
Think of a large body of saltwater ('sea') combined with the liquid we drink ('water') — that's what seawater is.