[Maritime Q-Scout]

Here's a thought, candidates can't kill themselves. Jin staying with Sun means he's committing suicide, something he cannot do. Perhaps in the death scene of his hand floating away was actually Frank saving him, and then bringing him to surface and to shore?

Sun however was stuck from the blast, and therefore would drown in the water.

*apologies if this is the spoiler in white a few posts earlier, I didn't read it as I don't want to know any actual spoilers merely theories of what may happen.