SWSA had a trackless train called SeaWorld Express during their Christmas Celebration. I found blog post with pictures of the train from 2012 and 2016. I'm surprised that they haven't brought this back, since it would be great for families.
Here is what it was like going on the train, according to a blog post:
Photos Source: SeaWorld San Antonio Christmas Celebration
Photo Source: Lighted train ride. - Picture of SeaWorld, San Antonio - Tripadvisor
Here is what it was like going on the train, according to a blog post:
Source: Saving for a DreamBefore boarding the train, each child received a ticket (that looked like the ticket in the Polar Express movie) and the tickets were punched once we were inside the train. The train took us around some Christmas decorations near the lake.
Photos Source: SeaWorld San Antonio Christmas Celebration
Photo Source: Lighted train ride. - Picture of SeaWorld, San Antonio - Tripadvisor