
We've done that - the Marine Observation Outpost (MOO). Last DL visit I went down in the sub with sister and her two little ones, and was glad we were near the hatch rather than at the far end of the sub. This is before the Chilean miners were rescued, mind you, so claustrophobia was on my mind.I get a little claustrophobic when it comes to the subs. I can sit through the ride, but I'd prefer not too. On my last trip I did try the "Outpost" where you watch a video of what the people on the ride see in a room with 2 benches and some space for a wheelchair. If you don't think you can do it, just go to the CM at the front of the queue and ask about the outpost and they'll get you in.
I just lean into the window really close so I feel the air in my face and so I can see the top of the water easily if I need to. It's really a fun ride so I suggest you try it, just ask to get on last and then have someone you're with sit next to you, then you've got the open area of the stairs on one side and someone you know on the other.
Of course if you decide it's not happening ask the CM at the head of the line to direct you to the handicapped viewing room. It's the same as the ride only you're in a room and not "under" water. 
Probably because you can see at all times, and the sub itself is not confining (it fits X number of people, it's not like the trunk of a car or an old-school MRI for example
) Not a huge fan of the ride, it's really long and not worth a huge wait IMO - but we'll hop on it if the line is short and we're walking by it 
See, for me it was never about being 'submerged', but how close you can get packed in there. That was the horrible part that I don't want to experience again, lol.

CRAMPED?........ To say the least, especially for a person that is 6 foot 2inches.
BUT, to me it was worth it. Anything at DL is worth it. We have gone on it severval times, and each time fine/see something new.
The tip of leaning into the porthole and letting the air hit your face is a good one. That way you can focus on looking out the porthole and not into the "sub" itself.
And unless you are a very small person, you will be touching your nieghbor in one way or the other, ie: kness, elbows, hips....

See, for me it was never about being 'submerged', but how close you can get packed in there. That was the horrible part that I don't want to experience again, lol.