If you could post a couple of photos, we might be able to ascertain whether the bird is truly a swan or maybe, a baby pelican. They would be the same color. It would be extremely difficult for the swan to survive in the gulf as the swans found in North America do not have a gland to separate the salt from water. If it is a swan, it would be extremely critical to try and get the bird out of the gulf, however, if it can fly, then, it would be very difficult to capture the bird. Most birds able to fly will usually find a fresh water supply. The Regal Swan