Enormous triangular craft. No lights, no noise.

I was taking some classes at the University of Houston during the summer and there was a summer pool party at night. My room mate was telling my others friends a joke. I was bored and looked up and saw this enormous triangular shaped craft. I would estimate to lenght to have been 1/2 mile. It was totally black, had no lights and made no noise. I screamed "Look, look". Only the girl sitting next to me looked up. I asked her "What was it ?". She made a face of "Idon't know" and turned her back to me not wanting to discuss it. It has been 17 years now and I hope I will know what it was before I die.