Complex sentence: At first, both continue to argue about how dumb the plan was, but are joyous when they realize they aren't shackled together anymore, but their joy is short-lived when they look down and notice they're now connected by leg via a pipe.
Split into simpler sentences: At first, both continue to argue about how dumb the plan was, but are briefly joyous when they realize they aren't shackled together anymore. However, they look down and realize they're now connected by leg via a pipe.