Preheat oven to 375 degrees. Mix ground beef with water and milk in a large bowl using your hands until beef is evenly moistened. Mix bread crumbs, onion, dulse flakes and egg into beef mixture until evenly integrated. Form beef mixture into a loaf.
Transfer meatloaf to a deep baking dish; tent with a sheet of aluminum foil. Bake in preheated oven 1 hour. Remove foil tent and bake until no longer pink in the center, about 30 minutes more.
