As far as Sea Base Alpha is concerned, it was a very clever way to present what is primarily a giant aquarium. It wasn't, in my mind, an effort to point out that in the future there would be a zillion of these under the surface. If we get honest, you can watch fish swim around in a tank just so long before you go brain dead. This was an interesting way to introduce it. The Hydrolators were shear genius. Want to know why I think that they no longer exist? Because it was a genius creation and the folks, that primarily keep their I.Q.'s in a thimble, actually believed that they were submerging and returning. They have had lawsuits brought by people that decided that the change in pressure from one level to another caused them medical problems. It wasn't worth it to keep in operation, plus they might have been getting to the point of disrepair as well. The system could have continued working with this theme as a nice little fantasy part of the pavilion. It was nice that Nemo gave them a reason to reinstate the sea cabs and the introduction of the characters helped to "educate" kids in a way that they really didn't know they were being educated. Nemo was just a different Hydrolator.