Fish Joke (Twice Told)

SHORT VERSION --
Question: What did the little fish say when it hit its head against the concrete wall?
Answer: Dam.

LONG VERSION (which happened yesterday; and yes, Ross is an adult) --
Jeff: What did the little fish say when it hit its head against the concrete wall?
Ross: (looking at Sandy for a hint)
Sandy: Oh ___ ...
Ross (moving his lips like a fish, and turning to Jeff): OH-WOH-WOH.
Sandy: No, Ross. That's not the answer. It was Oh-Something.
Jeff: It wasn't Oh-Something. Ask me the question back, Ross.
Ross (thinking...): What did the little fish say when it hit its head against the cement wall?
Jeff: It wasn't a cement wall. It was concrete.
Ross: What's the difference?
Jeff: (Gave explanation of the difference)
Ross: Oh. Okay. So, what did the little fish say when it hit its head against the concrete wall?
Jeff: Dam.
Ross: (Mouth dropped open and eyes popping out of his head at Jeff saying "that word.")
Sandy (laughing): It's a three-letter word, Ross, not a four-letter one!
Ross: Oh-h-h!