I don't see an air intake/engine, and that's not shaped right to be an HGV. So if it's something actually built for the military, it's gotta be a mockup. It does look similar to some NGAD concepts. Could be a full-size or 3/4 scale loyal wingman design. But if it was any of those, it would be under insanely tight security, and it's not, so maybe it's for an aviation startup.
It's probably not a boat, because it wouldn't be steerable with such a tiny rudder/keel in the middle.
Does anybody know where this was taken?