Strange black object flies inland from ocean preceding sunrise

My girlfriend and I walked out to the beach this morning to watch the sunrise. It was approximately 15-20 minutes before actual sunrise, when the sky was just lighting up, very clear out, we were standing in front of the Westin on A1A just north of Las Olas Blvd.
We got to the water's edge and after a couple seconds I looked up and my eyes immediately fixated on something moving across the sky.
It's very difficult to describe what we saw. The object was black - at first I thought it might be a bird very high up, but I couldn't discern any wings flapping, it just looked like a solid object moving slowly over the ocean, over and past us and continuing inland. There were no flashing lights, and as there were quite a few planes on the horizon, it was quite easy to see that this was not one of them. It was hard to focus on also, it seemed far away but quite low at the same time; for a second I actually thought it sort of looked like a person flying, but I dismissed this for obvious reasons. My girlfriend described it as "an asymmetrical rectangular blob floating westward, not like a bird that varies direction and flaps its wings, but more like a balloon".
Very creepy, no sound at all, and again this thing flew in from the ocean, maybe 1,000 ft (?) up, and proceeded inland. There were several planes on the horizon, several miles away and clearly discernible as conventional aircraft. The object that passed above us most definitely was not.