I got light throughout the dark cave but lost fire flies somewhere at or before the jump over the small water fall in the mountain so the last (?) cave stays dark. Several new attempts to bring up the flies to that cave go astray every time I try to jump into the first cave with the main falls....??? What is wrong?

I know it sounds odd but I found you can jump once with the fire flies so save the jump for that final water fall. Use barrels from the hidden cave above (pushed out the the water below) to build a bridge for the stream below. This way you don't have to jump that stream. I spent a looong time doing this. Knowing what to do is a lot easier than actually doing it. Don't bother trying to push one of the barrels to that final water falls...that's also a very frustrating attempt. Hope this helps.

Mordack

Which hidden cave above? The one I found behind the big wooden door did not have any barrels nor do any of the barrels in the cave below move, in fact I cannot find anything I can move. I am really stuck. Help.

Look a little closer at the area above that big wooden door. There are actually two areas up there. You need those barrels!

Dadguy

Have you taken a refreshing walk through that waterfall and out into the pool?

Mordack, thanks but your answer leaves me a bit puzzled.

So, first small stream has already been barreled in an early state. I can still pass it without losing flies.

Now, I have to try to position also one or two barrels to enter the first cave as many times as I wish with flies? With the falls so close by I doubt if I will get the barrels in stable position ... but worth trying.

Finally, can I get the flies to stay with me when I jump the small stream of the mountain path or must I build some bridge there first? Yep! I did bother trying to get a barrel there and, as expected, it can't be fixed to the position there and drops with the fall.

Footprint....Spoiler..

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you have to drop 2 crates, (barrells, lobster traps, whatever) from the caves above, then place them at the area where you jumped over the water to the cave the 1st time....then you can walk over the brook , then walk over the 2 barrells to the cave, then go up and jump the stream and still have a few glow bugs left...hope this helps.....
Paul