Monumental patience and an abundance of wit and humor !
While agreeing with the first two comments--I will add: a strong sense of "empowerment." In essence, possessing the ability to not readily panic nor emotionally crumble under adversity. I guess it sounds cliché but where does one go to take time for one's self when under duress? Having a strong mental fortitude is high on that list--- That is what I see.
Willing to make a life saving effort on the last breath of oxygen. Also be able to equally excel in physical or mental work.
Diplomacy, ability to do team-work,will-power, heightened degree of curiosity,amazing self-control and coolness even during life-threatening situations and an overall emotionally, mentally and physically well-balanced person !! :)