The title of this episode of course refers not only to a sea-faring vessel (as in the submarine) but also to Cas being Lucifer's vessel.
We delve into more Men of Letters lore, with all the Nazi/WWII stuff and the Hand of God. I did enjoy seeing Dean go back in time and wearing that uniform (*grin*), but of course can't help being disappointed that Sam never gets to go (and Sam himself didn't seem too happy about that either). Although how would he be able to pass himself off with his long hair, unless he hid it somehow or....*cries*...shaved it off. It was annoying having to see him basically play babysitter to Casifer. He done good in the end, though, and I'll come back to that.
Speaking of Casifer, he still makes me cringe. I actually felt bad for Crowley for a little while there. I thought Casifer's petting him and calling him "doggie" was over the top. And his facial expressions...first the creepy smile when Dean was telling Sam he needed to stay behind, and then the cheesy grin or whatever when he finally revealed to Dean (the "cat's outta the bag" line) who he was just made me LOL at how painfully bad they were.
The girl Dauphne (Daphne? However it's spelled), I really liked her character and how she decided to sacrifice herself for all of them. The guy who was keeping an eye on Dean & asking all the questions about the future...is it me, or did that actor look very familiar? He looks like he was in at least one other SPN episode. Maybe not, but he seems very familiar to me.
Sam wants so badly to save Dean, and apparently "Cas" needs to touch his soul. Ugh, I feel like I want to smack Casifer for duping them all this time to begin with. And Sam's face (and near tears?) when he realizes it's Lucifer... :( After touching Sam's soul, was that really Cas trying to hold off Luci like Sam did in Swan Song before he leaped into the pit? I guess it was, and I'm sorry but what he said to Sam just makes him look like such a coward for having said yes to Luci to begin with. I'm actually glad the Hand of God was good for only one use, even if it might've seemed a bit convenient. And I love how Sam still managed to save Dean by transporting Casifer away with the blood sigil. Go Sam!
Nice little brother moment at the end on a dock. Dean doesn't want to talk about the whole thing, and he still seems unhappy about the fact that the submarine sank after all.
That's about all I've got on this one. Maybe I'll have more thoughts on it upon rewatching.