水泄不通 [- - bù tōnɡ]... even a drop of water couldn't leak out [trickle through]; (to besiege ...) so closely that not a drop of water could have trickled through; be watertight; tightly packed; jam:
•¶ 挤得水泄不通 crowded so tightly that you can't move; be packed with people
•¶ 包围得水泄不通 so closely surrounded that it is impossible to break out