In a baking dish, mix together ¼ cup lemon juice, 1 tablespoon olive oil, sea salt, and ginger. Add the fillets, toss lightly to coat, and let marinate for 10 minutes, turning once.
To prepare the braising liquid, heat a large skillet, add the remaining tablespoon of oil and sauté the garlic, mushrooms, and scallions, with a pinch of sea salt for 3-4 minutes.
Add the broth or water, Braggs, dulse, and additional 2 tablespoons of lemon juice. Bring the mixture to a boil, turn down the heat, and simmer for 2-3 minutes.
Add the fish to the skillet with the braising liquid and spoon some of the braising liquid over the fish. Cover and cook over medium heat for 6-8 minutes, or until the fish flakes when tested. Garnish with chopped watercress.