"This is not a skill that's automatic, " Mullen said in a telephone interview.

CNN: Fatal wrecks underscore risks for young drivers

"There is a certain amount of luck involved, as well as the skill of the crew and the preparation of the boat, " explained Jarvis, in an interview before he left for the Antarctic.

CNN: for

"You really need someone who is a renaissance person with a tremendous range of skill, both political and substantive, with a deep reservoir of knowledge, " Burns said in an interview.

CNN: Obama nominates John Kerry to be secretary of state