Assuming you arrived from the right entrance by way of Route 14, you will arrive on top of a waterfall. In fact, you will fall straight down unless you move in some direction. There are just two hopping enemies at the top of the falls. Drop down to the screen below.
(If you happened to arrive here from the left, you will be greeted by a lot of hopping enemies. Proceed to the right through the forest, where you will encounter birds who fly straight until you pass beneath them, and then they drop down to attack you. Towards the end, the birds are replaced by slowly falling enemies who bounce high. When you reach the waterfall, more hopping enemies appear.)
When you are standing in front of the waterfall, drop down one screen further to reach the bottom of the falls. Assuming you rescued Faysha from Route 17, Bang will notice a statue which should indicate the entrance to the hidden passage that takes you to Route 35 where the Hermit has been kidnapped. Remove the hopping enemy and proceed to the statue. As soon as you get close enough, you will be transported to a tunnel. Be aware that as soon as you set foot in this tunnel, you cannot return to Route 6.
You start on the right side of the tunnel, and must cross a large body of water to reach the exit on the right. Although there are platforms above the water, you can easily swim through it. Some of the platforms contain gold, but you can leap high enough out of the water to collect them if you want to. (Just remember that every time you land back in the water, you spend a little time submerged and lose a small amount of health.) There are enemies swimming along the surface of the water, so be sure to fire continuously to the left as you swim in order to remove them. Hop out once you reach the left side and pass through the exit.