As far as a best time, that's up to you. It's hit or miss with the weather. If it's too windy they will cancel it. It could be windy in the morning and then nicer in the afternoon, or vice versa. When we did it, it was late in the afternoon. It was good for us as we got a full day of CC in and then headed to the boat for the excursion. Afterwards, we just headed to the ship. It was a nice way to end our day at CC.
I'd book the reservation before you go as it can sell out quickly. You can always check the excursions desk onboard if you want to change your time.
You do not get "wet" parasailing. That said, they will most likely dip your feet into the ocean. However, you're only wet up to about your knees.
Yes, you can take a camera. I'd recommend a waterpoof digital, but I saw several on our boat take regular digital cameras or camcorders with them. I took a cheap disposal water camera and was very disappointed with the picture quality. I wish I had taken our digital camera.
Getting your feet dipped:
Heading up. You take off and land on the large platform on the back of the boat.
Toward the top:
