@F'x (1) "*what's the verb describing how a fish moves in the water", that sounds like a much more valid question already*" - Okay, what if I didn't drop "in the water" in the end of that question and, thus, phrase it like this:
"What words would you insert here to complete this phrase "It was a usual day: birds were flying, men were walking, snakes were creeping and the fish were *** *in the water*?"
Would it still be open-ended? Note, it's exactly how I phrased my original question - the context was provided on both sides of the blank.