I don't know how to fix the dent. A guy in Lonsdale advertises aluminum boat repair. I don't know anything about him though.

However, once fixed.....there's some stuff called GLUVIT.....an epoxy type brush on stuff.......that makes the bottom slicker than owl snot, and sort of covers up imperfections, etc. I used it on a project jonboat that I'm working on......and was impressed.