Toothpaste for the windows
If you have a plexiglas window that has become foggy due to UV elements, age, etc., try this. Use toothpaste and a rag, and a good bit of elbow grease, to make the window clear again. It should look as good as new. Put a little of the toothpaste on the rag, a good terry cloth one, and rub hard. Use another towel to buff it shiny.
This can also work on car headlights. I know that they sell product especially for this, and maybe those would work on your boat as well. I used toothpaste on my Toyota head lamps that were dull, and a little yellowed. They are perfectly clear now, and shiny.