Congrats! We are getting married in Sea Island in June 2010!
There is a little Inn that is right across the street from the beach called the Sea Gate Inn. They own an empty lot that faces the beach. We have reserved rooms there for our wedding, and when we spoke to them, they said that if we wanted to have the wedding in a tent across the street on their empty lot, that they offer that to people who reserve all 24ish rooms in at the Inn for weddings. We already had a venue, so we werent able to take advantage, but it sounds like it might be exactly what you are looking for. You could get married on the beach and then walk up to the tent and still be right on the water.
There is another Inn right down the street from the Sea Gate (Ocean Gate or something Ocean) that has a top floor open air room/patio that they allow people who rent out the place to use for weddings. Same idea... you could get married on the beach and then walk back across the street to the Inn for the reception.
Hope this helps!! Good Luck!
Written on Oct. 26, 2009