There's also the scene in which the more Jerkass scientist Mark needs to be talked down. Lucas does so by holding a knife to his throat while sporting a very broad smile. Note that Lucas has been completely friendly and deferential up until this point: but once his authority as captain is questioned...
The Creature itself is pretty badass when he needs to be.
The suit itself was a triumph of special effects for the time, and still looks good today.
Special note has to be given to Ricou Browning, currently the only surviving original Universal Horror monster actor. He played the Creature in all the water scenes across the three films, having to swim, fight, and act whilst in a heavy aquatic special effects suit while holding his breath for minutes on end.