We didn't actually stay at the Sonesta but many people have asked about it. Sonesta is known for having it's own private 40 acre island.
There are actually two separate Sonesta buildings which are about a block or so from each other. Make sure you know which one you'll be staying in. On the main street is the Sonesta Resort and Casino which has a 2nd floor pool over looking street. Just down the road next to the Seaport Mall is the Sonesta Beach Tower.