I have thought of something else. This I think is from the late 1990s. It was a tank that had mermaids and maybe pirates too. Can't remember many details. I think it might have had oher underwater creatures too. I don't remember much about the figurines but the main thing I remember is that the tank was filled with clear gel- very gooey gel- to look like water.

Wonder World Aquarium? I am having problems finding more than a lawsuit about it though.

That might be it but I'm not sure.

Yes I think you're right! I just found a commercial on you tube. Thanks cat1864.