Should use 'no one' instead of 'nobody' on the last line because it has one too many syllables.

Correction. Your rhythm in the first, second, and last line should match.

'Cause down there no one could tell

Is more rhythmically correct.

One of the rules of a good limerick is a very strict rhythm.

Thanks, professor. I considered "No one." To me, the rhythm holds up. I 'll look at it again.

My only other limerick

There once was an old man from queens
who thought he had wonderful genes.
From his solid gold shitter
He ranted on twitter
Now we're wondering what "covfefe" means.