That secret entrance behind a waterfall in the original Legend of Zelda meant that I've been checking every waterfall in every game I've ever played since 1986.
I have been playing the new game sea of stars and its an old school rpg. I check all the places and several have had chests behind waterfalls and it always puts a smile on my face when I find them there.
It can't be too secret, I'm mean I haven't even played TOTK and even I know about it.
Joking aside, I have been playing BOTW and I check every body of water and mountain peak I come across because theres usually something, but that's also because there's so many things to find. SNES games though, 99% of the time there's nothing, but everytime I see dark spot in the ground, I'm smacking the shit out of it in hopes i get a fat stack of bananas.