Yup, we bring all our own snorkeling gear (for our family of 4). But we have only done that for the cruises we drive to. I might think twice about lugging it along on an airplane. The excursions will provide gear.
Same goes for the golf equipement. I'd like to go golfing, but I don't want the hassle of bringing my clubs. They will "rent them" to you, and some of the excursions, golf equipment is included in the price. I don't like to play with unfamiliar equipement so I haven't tried that yet.
Carnival Cruise Lines:
Fantasy 90, Celebration 95, Victory 05, Conquest 05, Spirit 6/06, Freedom 6/08, Holiday 7/08, Victory 6/09, Valor 9/09, Dream 6/10, Splendor 8/10,Conquest 8/11,Magic 11/11,Triumph 4/12,Spirit 7/12,Freedom 11/12, Triumph 2/13 - The fire cruise
NCL Dream October 2006, RCCL Mariner OTS June 2007