The riddle says that the 4 men fell into the water. They wouldnt fall into the water if they were in a upsidedown boat wich tipped over the right way. Besides, if the 4 men were already in the water, they would still be wet.
1/1=1, sound logical. But my gues is that 1/1=?.
Wrong, it said they fell "in" implying in the boat, don't try to change the words.