1. Cut 1 cucumber into 1/2-inch-thick slices; set aside. Pass remaining cucumbers through a juicer; you should have about 3 cups juice. Set aside.

2. In a medium bowl, whip cream to soft peaks. Stir in horseradish and 1/2 teaspoon salt. Cover with plastic wrap, and place in refrigerator until ready to use.

3. Using a sharp knife, make shallow slits in skin side of fish. Heat oil in a large ovenproof nonstick skillet over medium-high heat until it is very hot. Season both sides of fish fillets with salt and pepper, and place in pan skin side down. Cook until skin is browned, about 5 minutes; turn, and saute until fish is cooked through, about 5 minutes more. Transfer fish to warm shallow serving bowls.

4. Add garlic and reserved cucumber slices to pan; cook over low heat until cucumber is soft and translucent. Add reserved cucumber juice and the thyme leaves; cook just until mixture is hot. Season with salt and pepper. Ladle cucumber broth and slices around fish; garnish with horseradish cream and thyme sprigs.