Rub charcoal under your eyes if you want to see clearly. Sports players also rub charcoal under their eyes to see nice and clear in the bright sun.
You have to have clear vision because you're about to go out in your row (りょう) boat. The light off the water shines right into your eyes and you need the charcoal to clear that up for you. Otherwise you'll end up crashing into the shore or going over a waterfall to your death.
Currently there are no similar looking kanji which exist in the WaniKani learning system