In the underwater scene when Rex blows up the ice pack, ice appears to be denser than water in this situation. The ice sinks when it's blown up, and even if there were pieces of metal on top of the ice, it shouldn't. Some pieces the size of a five-story building have no metal and still sink.
In the scene where Ripcord and Duke are in the transport and Ripcord pats Heavy Duty on the back and gets his arm twisted as a result, Ripcord makes a crack about Heavy Duty having a "Kung Fu Grip". This refers to some of the earliest G.I. Joe's action figures who were advertised to have the Kung Fu Grip.