Is this a good metaphor? "i am a softball, i won't stop till i reach the other side of the fence."

Yes, its good. But work on your metaphors more it'll be perfect.

A limerick is a piece that follows the AABBA format. That means that lines one and two rhyme with each other, three and four rhyme with each other, and line five rhymes with the first two. So, an example of a limerick about the ocean would be,

“There’s nothing that’s quite like the sea
With blue water deep as can be
All the shells on the sand
In the sun getting tanned
Nothing else could be better to me”

because sea, be, and me rhyme, and so do sand and tanned.