Let's be honest: There was never any real fear that Sam and Callen would die on NCIS: Los Angeles Season 6 Episode 1.
But there was a submarine that was turned into a bomb by terrorists, which placed our heroes in at least a unique life-threatening situation.
The premiere also excelled in having Sam and Callen react to their circumstance with the appropriate dread, sure. But also with a few doses of humor. It's almost as if the writers were saying:
We all know these two are coming out alive. But allow us to entertain you with how that actually happens!
And entertain us the episode did.
Sam and Callen's training/experience enabled them to recognize the extent of danger they were in, while still remaining calm. The terrorists were on a suicide mission to explode an aircraft carrier in San Diego... so, in response, Sam and Callen (Sallen?) announced their own suicide mission to prevent the attack.
The question therefore arose: Who's will would win out in the end?