Besides displaying just the usual weapons and other military equipment, this year's Beijing Military Expo also had an eerily realistic arowana fish robot that swims and behaves just like the real thing.
From OddityCentral:
It would swim around normally, and raise its head for a while whenever it reached a wall, then just wing its tail again and swim in another direction. At first glance, its appearance and movements were those of an actual fish, and it was only on close inspection that one realized this was an advanced fish-like robot.
In the clip, you'll also see a glimpse of what looks like a shark robot!