The better ones have a motor like the vibromotor on the original car to make the band go. It can be turned off. If you want to be able to turn off the operation, go with the modern, more expensive car, or else the gear-drive one. Keep in mind that there are aquarium cars by K-line & MTH.
There, is some misinformation here, I believe. 1) The motor-drive aquarium cars Lionel has offered for the last 10 years or so are nothing like the vintage vibromotor.... but use a can motor. 2) K-Line's "aquarium car" (I believe only two were released) were aluminum body-cars with actual liquid inside a sealed plastic container with floating, plastic fish. Very heavy! MTH's aquarium cars are virtually like Lionel's.... but all of theirs feature motor drive. All but the most recent MTH models, however, were plagued with "belt separation" issues.
