You can currently indirectly use your Marriott Rewards points to reserve Swan and Dolphin. You have to link your Marriott Rewards account to your Starwood Preferred Guest account (if you don't currently have one of those, you can create one off the starwood preferred guest website). You will then be able to transfer your MR points to SPG at a ratio of 3MR : 1SPG. Currently, the Swan resort is 12,000 SPG points for a standard room and the Dolphin resort is 10,000 SPG points for a standard room. So, it will take 36,000 MR points per night at the Swan or 30,000 MR points per night at the Dolphin.