While the bulk of the audience was either frozen or in flight mode, there was one notable exception. Of course that was Arjun. Arjun had grabbed his bow and his arrows. He didn't have to worry about accidentally hitting Dronacharya instead of the Crocodile. He was confident in his aim. Or maybe he thought that even if he hit Dronacharya it couldn't put his professor in any worse situation than he already was in. Either way, Arjun fired off 5 arrows and neatly sliced the Crocodile.
With the corpse of the Crocodile floating in pieces, the other princes finally calmed down. One Kaurav prince ventured so far as to suggest that the crocodile was large enough that they could all have new shoes made for the entire class. Even the Pandavas, why not?
The Princes were bursting with questions but no one dared to ask him. Why hadn't he tackled the Crocodile himself? He could pierce a twig with another twig as we saw in Couldn't he have turned a handful of water into a diamond sword or something? Or shoot a lightning bolt at the Crocodile? Or failing all that, couldn't he have just given the crocodile a lesson in angle of incidences and density of the water and aerodynamic coefficients? That would make it yawn for sure, and then he could have escaped.
Dronacharya answered the unspoken questions himself. Of course he could have done all that. He could have wrestled the Crocodile with his bare hands. But the moment he saw that the Crocodile was attacking he decided to test his students. And guess what, only one student had passed. Arjun had not panicked and he had done the most expedient thing – which was to defend his teacher.