Showers also help me to remember dreams or more of dreams than I am able to in the morning. I think it's due to a combination of two things: 1. the hot water relaxes, getting into a pre-sleep state (I guess that's how to word it), and 2. when I shower, I keep my eyes closed the entire time (it may sound weird, but try it sometime ) which I find allows me to get HI or even sometimes construct a world/scenario of my own, though not as detailed as in a dream. So I think between those two, my mind enters a sleep state, and as Puffin said, it begins "throwing dream memories at me, or making them easier to recall".