It's not a complete sentence. It might be okay in a casual conversation where both speakers know what the subject and object of the sentence are:
"What did John do with those fish?"
"[John] Ate them ["those fish"] down by the river."
The river and a bee was talking very free.................... the bee then swam down into the river and the river ate the bee
This river is navigable - means you can get your boat down it......
This sentence does: They sailed down river to the delta.
He ate tacos on his row row row your taco boat down the river :)
Ate is intransitive in that sentence. There is no direct object."You ate pizza in the cafeteria" is an example of ate as a transitive verb (pizza is the direct object).
what is the gerund phrase in this sentence, Floating down the river on a raft was not Joel's idea of fun.
In the sentence, "You ate an apple." the noun is apple, a word for a thing.
the duck has to quibble down to the river to survive!
In the sentence "Floating down the river on a raft was not Joel's idea of fun," the gerund phrase is "Floating down the river on a raft." This phrase functions as the subject of the sentence and describes the activity that Joel does not consider enjoyable. The gerund "floating" acts as a noun, representing the action of drifting on the river.
She slid down, quickly engulfed by the depths of the river.
I slithered down the muddy bank of Indus river.
The little creek flowed down the hill and into the river.