So I just exited Dawnstar Sanctuary when a dragon attacked Dawnstar. Being an assasin I used Dragonrend to force the dragon to land without revealing myself. Luckily, the dragon land across the cove, so I just sniped the ancient dragon with my legendary daedric bow. As soon as the dragon dead I swam across the cove to get the bone. Only to be greeted by an unbelievable sight of the dragon sinking into the snow! Has this ever happened to someone else? perhaps it's because I'm swimming during the dragon's death animation?