Twilight is crying because of the possibility that she might outlive almost everyone she loves. The way she is underwater implies that this is an unconscious or subconscious issue that plagues her constantly.

@Mirth
 
I’m glad you enjoyed it :)

@Ebalosus  
You know, after seeing you persistently promote that movie throughout most of the immortality blues-tagged stuff, I finally decided to just sit down & watch it, and see why you’re so gung-ho about it.  
And I’m really glad I did. It was incredibly fascinating to watch, and never lost hold of my attention. It was also nice to take a break from all of the “tragedy of long life” stuff & actually see someone who was, at the very least, content with their immortality.  
So, thanks for constantly spamming that image XD .

…Suicide by drowning? Dark.

Ahem!