Here's what I did (as I recall - couldn't find all my notes). On Raiatea we took the Snorkel and Black Pearl Farm excursion - (personally) you can skip the Black Pearl Farm but the snorkel portion was great fun. You can position yourself in the current and just "cruise" along, then get out, walk back up the beach, get back in, find the current and away you go again. In Bora Bora we did the Stingray/snorkel and that was GREAT FUN (more fun than Stingray City on Grand Cayman) because here there were reef sharks just a few meters away from us cruising back and forth - they only come so close but no closer. When you first spot them, the adrenalin really kicks in! After the stingrays they take you to an area where you can snorkel. On Moorea we rented a car and did our own thing. Some of the people I spoke to went to the shark feeding excursion and really enjoyed that. By the way - you can go on-line to www.rssc.com
pick your cruise date, click on each of the days/ports - that will give you a list of the excursions - click on each of them for details including cost. Also, don't forget that the ship has its own marina where you can get equipment and sign up for water skiing around the ship.
One evening before dinner, we were having a cocktail on our veranda and happened to look down and saw a huge sea turtle just below the surface swimming along parallel to the ship. That was special.
You are going to enjoy just looking at the water and the islands - they are truly magical! Hope this all helps.
Writing all of this makes me want to do it again!