Underground River                                      -      -     NE 
(-------------------------------------------------)     W <---(M)---> E
                                                        SW     -      -

As you flounder through this river, the deafening sound of water crashing
on the cave walls threatens to drive you mad.  The water is freezing cold,
and you wonder if you will manage to survive the frostbite which is no doubt
sinking deep into your limbs.  You notice a strong current leading downward
into the depths.  A current here attempts to suck you into a small
underwater tunnel leading downward.