Place the champagne in a large skillet and bring to a boil over high heat. Add the salt, scallions, and sea bass and return to a boil. Reduce heat to low, cover, and simmer 5 minutes. Add the cucumbers and cook 3 to 5 minutes more or until the fish just flakes when tested with a fork. Remove the fish and vegetables from the skillet and keep warm. Increase heat to high and boil the liquid in the skillet, uncovered, until reduced to 1/2 cup, about 5 minutes. Blend in the light cream. Spoon some sauce onto each of 4 plates. Arrange the vegetables and fish on top.