The real version that my friends and I sing at school is the following:

Down by riverbank of hankey-pank a bullfrog jumps from bank to bank sayin' eeps iips ohps umps down by the river bank- kerplunk!
1-2-3-4-5-6-7-8-9..... (and at ten whoever gets their hand slapped is eliminated. if they pull their hand away the person who slapped them is out.)