(ed: there are more along these lines on the 'crap limericks' page)

The boy stood on the burning deck
Picking his nose like mad
Rolling it into little balls
And flicking them at his dad.

The boy stood on the burning deck
His pockets full of crackers
One went off between his legs
And paralysed his knackers.

The boy stood on the burning deck
The oars were in the rowlocks
A spark flew up his trouser leg
And burned him on the... knee

(ed: there are many. many more verses to this one too!)