Scared of the Dark at 20

I don't really understand why a fear of the dark is considered a child thing ya know? I have a fear of bodies of water that I can't see the bottom of and I used to be afraid of the dark, it's pretty much the same concept of being afraid of not being able to see everything that might be there but no one has ever claimed my fear is childish like they did when I was afraid of the dark.

Im not nessessarily scared of the dark itself, but I get super scared walking alone at night, especially if I don't have my glasses on. I need to see where I'm walking or I'll look like a blubbering baby walking home