"The boat goes down the river."
Translation:El barco baja por el río.
We have many verbs in English that use go + preposition (go up, go down, go in, go out, etc.) and in Spanish they are almost always separate verbs of their own (subir, bajar, entrar, salir, etc). It's worth remembering that "ir" is never used with these.
It's that baja is coming from bajar, to "go down / descend" rather than meaning "down."
One of the options used desciende instead of baja. I got it wrong for marking it correct as well. Can someone explain why desciende doesn't work?
"Descendimos de la montaña por el lado oeste."