It might not keep you dry, but if you fall the other tourists will be able to see it and take lots of pictures for the evening news. There are also cheap sandals so you don't slip. Your own shoes go in a plastic bag that might keep them dry.
You go down in the elevator so you can climb up again. The Cave of the Winds has been gone since 1924, so the name is obsolete. Instead of a trail behind Bridal Veil Falls, there are a series of stairs and decks that take you in front of the waterfall.
The boat takes you to the base of American and Horseshoe Falls. You'd need a waterproof camera to really get good pictures! The water was blowing so hard into my face when we got close to Horseshoe Falls, I could barely keep my eyes open! And the noise was unbelievable right there...
We picked the absolutely perfect day to go. We got there before peak tourist season in June, so no crowds, no lines, no waiting. It was a warm and sunny day, so the sky and water were blue, and we dried off quickly. The wisteria and locust trees were in bloom, so the whole park smelled wonderful.
For lots more pictures of the waterfalls: Niagara Falls State Park (Let me know which one you like best.)