I am told I cried the first time
but When I was older I really dug the navy uniforms, the organ music, etc. I really liked the 20k movie
I too was a big fan of the 20k movie and I think that in part accounts for my displeasure with the attraction. The 20k movie won two Academy Awards and one of those awards was for special effects. Therefore I assumed (incorrectly) that the attraction would have special effects that were superb. And above ground that was true.
The subs looked spectacular. They were darn very close approximations of the Nautilus. The entire lagoon looked just like the mysterious island of Vulcania! And you could see the subs travel into an island cave between cascading waterfalls! My first impression was that this was going to be a wonderful adventure. It was all very convincing.
Waiting in the queue they played concertina music of various sea s
hanties such as Blow the man down, What shall we do with the drunken sailor and, of course, A Whale of a Tale from the movie. It was a great way to build the anticipation for the ride!
Once you entered the boat, you found water sloshing around on the bottom deck. It turned out that the hatches through which people entered and exited were not water tight. As a result, water would get in the subs from the waterfall as the subs entered Vulcania. They had to dam up the center part of the waterfall to keep the boats dryer. However, some water still got in the boats because it was always wet in there. The usual afternoon rains at WDW added to the problem as water would drip in from the hatches. But I think it also added to the effect of being in a real submarine because you had water leaks and water sloshing around on the floor!
Another part of the ambiance was the close quarters and lousy ventilation. When forty people were in a sub, you were packed in there like sardines. The A/C systems never really worked very well and there was no significant air flow. For me, I thought it was all part of the show to have the subs being hot with sweltering humidity. Submarines have very cramped space and the air quality can be very problematic. But people that were claustrophobic or didn't like the smell of other guest's body odor had rough trips.
The audio on the boats was terrific! The person on the PA system sounded just like Captain Nemo (James Mason) from the movie. Plus they had the spooky organ music playing in the background. It really did a good job of setting the mood.
After the sub left the dock it submerged and air bubbles would blow by the viewing ports. This was a simulation of air being bled from the subs ballast tanks and replaced with sea water to enable the sub to submerge. It was a very good effect.
Once the portholes cleared of bubbles the view through the portholes was disappointing unless you were a small child. Everything looked like plastic phony toys you'd find in a swimming pool or a home aquarium. You could clearly see the monofilament line holding the props in place! The special effects looked like one step below the day-glow cardboard cutouts in Mr. Toad's Wild Ride.
When is was time to surface, air bubbles would again stream by your porthole! That didn't make any sense. To surface, the sub would be pumping compressed air into the ballast tanks and expelling sea water. They wouldn't be wasting air blowing it out of the sub. It's just another case of Disney saying to their guests back in 1971, "They're tourists, what do they know"!
It was obvious that Disney had not yet figured out how to create or present convincing underwater stage sets. But in those days it was fun for small children so that's really all the mattered.