Mahé and La Digue are connected by this comfortable high-speed ferry which runs up to 3 times per day. If you prefer other timings, you have more options by taking a ferry to Praslin and change ferries there to get to La Digue.
Usually there is a short stopover on Praslin.
Get from Mahé to La Digue in less than 2 hrs.
It's a great way to enjoy spectacular views of the islands. See flying fish and probably even dolphins jumping, especially when you ride on the upper deck!