It is an elongated, comma-shaped estuary formed where the Ugashik River empties into Bristol Bay, on the western coast of the Alaska Peninsula.
Its waters are characteristically turbid and turbulent, the result of muddy feeder streams, frequent winds, and very high tides.
The southern shore is a shifting series of mud-and-sand ridges, the northernmost and most prominent of which is called South Spit.
Ugashik Bay's weather is quite variable, especially during winter when storm systems frequently change climatological influences on the area.
Westerly winds blowing off the Bering Sea bring high humidity and biting cold, combined with coastal low clouds and fog, even in summer.