Nemo is devoted to his crew and grieves deeply when members are killed after a mysterious collision with a surface vessel or during a giant squid attack in the Caribbean Sea. He is equally compassionate in his treatment of the castaways in "The Mysterious Island", also retaining a deep attachment to his deceased wife and children. Despite these tragic losses, he rarely expresses his anger. Moreover, he is a man of immense courage, taking the lead in every emergency, from fighting sharks and squids to releasing the "Nautilus" from Antarctic ice—an ordeal that entailed reduced oxygen stores and consecutive eight-hour shifts. Aronnax also credits him with discovering Atlantis.