triangle slowly moving object with "lightning" emitting from the front of it

Years ago, I believe it was the summer of 1993 my wife and myself were headed out to my favorite camping place (Woodward Reservoir in Oakdale Ca.) to meet my parents who were already there. We pulled into the campground around 10 p.m. and proceeded to try to find my parents.
As we were trying to find them, we both noticed a large aircraft over the water near the 28-mile Road Bridge. It was triangle in shape, and very large, maybe 200 ft wide. It had no sound, was maybe 100 ft off of the water, and moved very slow (10-15 mph). There were white lights at each corner of the aircraft, the lights were not particularly bright, nor were they dull. They had a warm fuzzy "glow" about them. As if this wasn't amazing enough for us, there was what appeared to be lightning bolts shooting out of the front of it. This lightning came in pulses lasting about 5 seconds each, and maybe 10 seconds in-between each.
We watched this for 15 to 20 minutes before we were both so freaked out that we went into town to get a hotel room for the night. It is important to realize that both of us seen this thing. Neither of us was drinking, or on any drugs, and even 14 yrs later our individual accounts of what we seen that night are the same.
I have searched for similar accounts online, but have so far not been able to find anything.
Witness indicates that the date of the incident is approximate.  PD