I was expecting more of a dark, bubbling reverb for 'underwater'. I listened to the solo a few times when you first posted this. It sounded like an 1/8th note pre-delay, followed by a brighter medium-length reverb that was fairly wet. You should be able to get this with any of the Room, Hall, etc. algorithms.
I never tried to actually duplicate it. If you've found your answer already, that's great. If not, here's a friendly bump to get another look at it.
