While in Oahu, my girlfriends and I booked the snorkel tour to Turtle Canyon on the Holokai Catamaran.  The catamaran boards at Outrigger Reef.  Before you jump on ship, they have a photographer take a group picture for you that is available for purchase at the end if you like.  Ours turned out super cute and half of our party ended up buying it (me included).  The boat is spacious, comfortable and clean.  The staff on board is really fun and friendly.  There is a snack and water included.  Alcoholic beverages can also be purchased on board.  We did a sail first as there were too many other catamarans at the snorkel spot.  I think the captain said that they usually start off with the snorkel and end with a sail.  The sail to the middle of the ocean was fun and relaxing.  Everyone was laying out on the nets and suntanning or up against the railings taking it all or snapping photos.  There was a just a chill vibe on board.  Our group was in high spirits, enjoying the sunshine and beautiful views of the shoreline and Diamond Head.  There were smiles all around.  We eventually got to the middle of Turtle Bay for some snorkeling and it was amazing.  You could see an abundance of  large sea turtles and ton of fish.  So very cool.   A life jacket and snorkel gear is provided to you as part of the tour.  You’re out there in the middle of the ocean for a fair bit of time.  Once we got back on the boat to head back to shore, the water got very , very choppy.  Unfortunately, half of our group ended up getting seasick (even those who normally don’t) so that was a downside.  I would suggest that you take some Gravol with you just to be on the safe side.   All in all it was a great 2 and a half hours and a happy memory.