We did the glass bottom boat ride in Nassau in 2002 on the Wonder. I loved it. I really didn't care so much for looking under the boat at the fish - not that that was bad, it wasn't, they did show you some kind of wreck or something, I really can't remember what it was. We took some photos of the underwater things.
I really loved riding around on the top deck with the breeze blowing across my face, looking at the beautiful islands and hearing a little history and having the houses of famous people pointed out.
I guess it would depend also if you were traveling with children. We weren't (we were 6 adults) so I can't really say how a child would enjoy it. To this day, it is one of the highlights of that cruise for me.