That is quite an impressive sub! Rated to 1200' depth, wow! I wouldn't think a trailerable unit that small could do all that.
So it's a 1-man, dry, 1 atmosphere sub. The one at DDI does not have the manipulator arm or the scanning sonar (at least not in the pictures) and has "Alpha" on the side.
All sorts of possibilities to ponder about why it's parked at DDI.
Scroll down to the middle of the page and look at the sonar section. I think we do some focus reading on the sonar ability of the "Delta's Imagenex 881"