Subject of Spelling

In a train carriage one day were two small boys and a middle aged woman reading a book. The two small boys were having a deep heated discussion on the subject of spelling.

"Its spelt ' W-W-W-W-O-O-O-O-M-M-M-M-B-B-B-B '"

"No its not. It's spelt 'W-W-W-O-O-O-O-O-O-O-O-M-M-M-M-M-M-M-B-B-B'"

The lady leans over and says "Excuse me, but I think you'll find its spelt 'W-O-M-B'".

First little boy replies " Nah, I bet you've never even seen a hippopotamus, never mind heard one fart underwater !"