Located directly across from Mr. Toad, 20,000 Leagues was always a must for my family. I remember freaking out as a kid thinking we were actually diving into the depths of the ocean.Though it remained popular throughout its existence, it was closed on September 5, 1994, for what was called a temporary maintenance period. The closure was officially made permanent in 1996. During the grand opening of Ariel's Under Sea Adventure water from the 20,000 Leagues lagoon was poured into the new grotto as a tribute.
Here is a great article about the closure of this legendary ride