Arrow-shaped balls of light.While driving south on highway 1806 along the Heart River south of Mandan, North Dakota, on a clear and sunny afternoon, I saw through the front passenger window 11 or 12 luminescent pinkish-orange balls of lights arranged in the shape of an arrow--as in--(approximately, but not exactly) * * * * * * * * * * The formation of lights, maybe fifty to a hundred feet in length, was coming down at an angle, moving slowly, toward the river, which was probably two hundred yards from the highway.My view was blocked temporarily by a stand of trees, but seconds later, having passed the trees, I saw the formation again. It was headed into the river and one by one the luminescent balls of lights went into the water.There was no other traffic to cause a reflection. No planes were flying overhead.Upon arriving home, I immediately made notes and a drawing of what I had seen.((NUFORC Note: Witness indicates that the date of the event is approximate. PD))