A professor is installing lights that do not affect the zubats inside cave, so Flash is not required. Beyond the lake, the north professor claims he is still installing the light for the deeper part. The south professor blocks the way for no obvious reason.
The north professor in the past has finished installing the lights for even the deeper parts. There Wobbuffet (gold version) or Teddiursa (silver version) appears. The south professor is gone too, giving way to Route 46.
Pokemon Found Here
|Dunsparce||G||S||M||D||N||Land||*Appears randomly during battle (in past)
*Appears on the eastern part of cave (in present, need Surf)
|Teddiursa||G||S||M||D||Land||*Appears only in the northern part of cave (in present, need Surf)|