Who was Ned Land in 20,000 Leagues Under the Sea? What was his opinion about the narwhal? Why did he think so?

In Jules Verne's 20,000 Leagues Under the Sea, Ned Land is described as "the prince of harpooners." Professor Aronnax befriends Ned Land quickly, saying that while Ned did not talk very much at the outset, he "who calls himself Canadian calls himself French . . . My nationality drew him to me, no doubt." Ned is introduced thusly:

Ned Land was a Canadian, with an uncommon quickness of hand, and who knew no equal in his dangerous occupation. Skill, coolness, audacity, and cunning he possessed in a superior degree . . . Ned Land was about forty years of age; he was a tall man (more than six feet high), strongly built, grave and taciturn, occasionally violent, and very passionate when contradicted.

As for his opinion on the narwhal, Ned does not believe it exists. By this point in the novel, it has been discovered that ships have been coming into port with large tears in their hulls, "in the form of an isosceles triangle." The probability of this being caused by a narwhal is in fact low. Ned claims that this is because there is no part of a living narwhal, or any cetacean alive, for that matter, that would be able to penetrate the iron hull of a ship. He tells the professor that if the ship were made of wood, perhaps it could happen.
At first Professor Aronnax is astounded that Ned does not believe in the existence of the narwhal, given his professional harpooning abilities. But then, Aronnax points out, this animal would have to be extremely strong, and exert a great amount of pressure, to be able to cause the damage. Ned says that perhaps this animal is covered in armored metal plates like a frigate. By the end of this exchange, Ned is not convinced of the existence of the narwhal but says that "if such animals do exist at the bottom of the seas, they must necessarily be as strong as you say."