The first public discussion of the Hyperloop was in http://pandodaily.com/2012/07/12/pandomonthly-presents-a-fir... starting about 43 minutes in. A revealing bit of the conversation a minute later went like this:
Elon: I have a name for it, the Hyperloop.
Interviewer: Is that like a Jetson's tunnel?
Elon: Something like that, yeah.
Interviewer: You just get in, it whisks you?
Elon: Um, yeah. Yeah.
He later on said, You're guessing in the right direction.
This suggests to me VERY STRONGLY that his technology proposal MUST be a tube of some sort. He also said that it could store enough energy to run 24x7 without using batteries. That implies that he's got a lot of material going very, very fast.
Interestingly this is the time that he made his 30 minutes downtown to downtown comment, and his solar panel comment, but said nothing indicating no right of way issues. Later on he said that he came up with a way to make it much cheaper, and to get rid of right of way issues, but hasn't been repeating the other comments that I know of.
This suggests to me that in July he might not have had right of way figured out, and suggests to me that getting rid of the right of way issues by putting it in the ocean might not be a bad guess as to the insight he had over the summer that dramatically reduces costs.
My proposal may not be on the right track. But I think it is safe to conclude from what Elon has said that it is a tube. It has a lot of mass moving. And I don't think it infeasible that he would be thinking about putting this in the ocean to solve the rights issue.