Marriott's OceanWatch Villas at Grande Dunes

My wife is a schoolteacher and several of her schoolteacher friends have recently bought into this resort. I said OK but it must be oceanfront. Also it must be in the Conch Villa, Scallop Villa or Starfish Villa. Besides buying directly from the resort how do I buy in the secondary market and guarantee it's oceanfront and in the Conch Villa, Scallop Villa or Starfish Villa.