use the hm flash.
the cave isnt too hard.
the dark cave can be entered on route 45 or route 46
Dark Cave
Dark cave.
You can find Waterfall in the Dark Cave.
you just go south of blackthorn city
in the dark cave near blackthorn city
Peunut butter jelly time
out of dark cave on route 30 there will come a hiker and he will give you it
In Gold and Silver Wobbuffet can be found in Dark Cave. In Crystal, in addition to Dark Cave, you can also get one at the Goldenrod Game Corner for 1500 coins.
I don't know how you could have missed it, but it is east of Violet City where route 31 and 30 meet. And yes, the dark, scary opening in the hill is the Dark Cave. There is even a sign if you get confused.
if this is the swirl islands . . <-- . . go to this one
go north to dark cave than west to violet city