How to get to Devil's Island from French Guiana?

We are going to go to visit French Guiana at the beginning of next year. I've been looking into a few side trips that we could do and there is one place in particular that really appeals to me. This is Devil's Island, the former penal colony. How should we get there from French Guiana?

Devil's Island is a popular vacation destination now - a lot nicer than it used to be, I am sure! The climate is great and the nature stunning. As for how to get there, what with Devil's Island being an island and all that, there is only one way. Guess what it is? That is right - by boat!

I always thought that Devil's Island was part of French Guiana! But if it is not it won't be the end of my world as I know it. I went there once and I found it very breath taking. And yes, I had to go on a boat to get there.
I do understand however that they used it as a penal colony. Must have been very hard to escape from there. It reminded me of papillon.

I am sure that Devil's Island is not part of French Guiana but that it is, in fact, like French Guiana (check the reference in its very name:)) part of FRANCE. So when it comes to the visa regime for Devil's Island, I am sure that it is the same as it is in French Guiana.