Go to this website: http://freeweb.siol.net/danej/riverIQGame.swf    
It's in Japanese, so to start, click on blue circle.
The IQ test rules are:

1. Only 2 persons on the raft at a time.

2. The father cannot stay with any of the daughters without their mother's presence

3. The mother cannot stay with any of the sons without their father's presence

4. The thief (striped shirt) cannot stay with any family member if the Policeman is not there

5. Only the Father, the Mother and the Policeman know how to operate the raft

6. To move the people click on them. 
7. To move the raft click on the pole on the opposite side of the river.