I recently did a liveaboard in the Coral Sea and we did a lot of drift diving where we'd be taken out in the inflatables and do our drift dive back to the boat. We all did backward roll entries into the water. A couple of people were worried at first but everybody did it. Just make sure you have a way to get back in the boat. You might want to try a practice or 2 with some help on the boat to work out the getting in and out of the water thing.