What was the plan of Professor Arronax to fulfill their mission?

Professor Aronnax is a leading marine biologist. His professional interest is piqued by tales of a deadly sea monster—thought to be a giant narwhal—that has apparently been terrorizing international shipping lanes. A number of ships have been destroyed, which has severely disrupted the flow of trade. The American government has become so concerned that it has put together an expedition to hunt down and kill the dreaded sea monster before it wreaks any further havoc.
Professor Aronnax is just the man to take part in such an expedition. With his vast knowledge and expertise, he is ideally placed to identify this strange and deadly creature. Once he has done so, he will gain the credit for discovering what he believes is possibly a giant mutation of a narwhal. Professor Aronnax will be feted all across the world for this remarkable scientific discovery; his place in history is assured. No wonder he regards the expedition as his sole purpose in life.