I think how you feel is actually a perfectly normal human aversion to being trapped in a closed space. I did, however, complete the Disneyland submarine ride without issue!
Hence my use of the term “moderate.” I’ve toured two submarines and I, too, completed the Disneyland ride (and damned proud of it!) . I think the key thing for me is knowing the length of time of confinement. I need to sit in aisle seats on planes, or middle or window, if the adjacent seat is empty