Subject: Why can water pass over cell membranes (the phospholipid bilayer) so easily

I am doing A level biology and want to understand how it is possible for 
water molecules to pass over the phospholipid bilayer in a cell membrane.  
I understand that the middle of the bilayer, where the fatty acids are 
found is not charged.  This would mean that a charged molecule like water
(which is polar)would not be able to pass through very easily.  However it 
cannot, and I want to understand why.  My teacher does not know the answer 
and I have looked in various encyclopedias and A level text books, please 
help.

Re: Why can water pass over cell membranes (the phospholipid bilayer) so easily