Saw a craft at night illuminating Puget Sound water with two beams of light from high up just off Vashon Is near Three Tree Point.At about 22:57 my girlfriend, 32, (who is an medical imaging office employee), asked me what it was out over the water between our home (we live in a cottage about 200 ft above Three Tree Point and back about .5 miles from the tip of the point - we are in direct line with it with our back view windows pointing directly west toward Vashon Island) that was flashing light illuminating the water. I looked and first to mind it was a helicopter - but we could not hear it as we typically do for the Life Flight helicopter at the same distance and approximate altitude - which for the object we saw was about 8K feet above the water. I am a component engineer in the electronics design industry and am 46. The craft stayed - not hovering with movement - in one place and had two lights shine down to the water in cone shape with the wide part of the cone illuminating the water. The craft appeared to be a helicopter but had no wop wop sound. It shined a light toward our direction in the direction of east that was very bright as if to hide the outline of the craft while lighting up the water in an alternate sequence with each beam lasting about 2-3 seconds before switching to the other beam and often more rapidly then that. There were two red lights seen on the craft separate from each other but close - if it were a private plane the red lights were about 10 feet apart. We watched the craft stay in one place doing all this for about 2 minutes. It then turned off the beams down to the water and the light shining east and came slowly east toward our direction for about a minute or so as if on a tightrope and then turned southerly angling toward Seatac airport at which time I saw a strobing white light in front of the craft, the two red lights, and then heard prop sounds typical of prop private airplanes and it continued flying toward Seatac. It was about 23:01 when I called the Burien police and told them and then called the Coast Guard at their prompting to tell them what we saw. I could not see the outline of the craf! t becaus e if was too dark outside. There was no green light on the craft at all.((NUFORC Note: We spoke with this witness at length, and found him to be sincere. He was familiar with the lighting pattern on civilian and military aircraft. We express our gratitude to the U. S. Coast Guard Search and Rescue office in Seattle for forwarding the information to our Center. PD))