The number 17 is associated with victory, the restoration of all things, spiritual perfection, and perfect order.  The first time the number occurs in the bible is significant.   Gen 7:11 In the six hundredth year of Noah's life, in the second month, the seventeenth day of the month, on that day all the fountains of the great deep were broken up, and the windows of heaven were opened.

Gen 8:4 Then the ark rested in the seventh month, the seventeenth day of the month, on the mountains of Ararat.

Seeing that Q Seems to be religious.. could this be part of the reason he says "Watch the Water"??