We did this excursion through Disney, and had a little over 3 hours (so I guess it must vary depending on how quickly organised the group gets through the different stages of the trip).
It is a wonderful place, BUT just no where near enough time.
The underground/ and semi underground (there are two routes) river trek is unmissible........ but the time you have done this you have lost another hour, and then it is lunch....leaving only around 1.5 hours to get round the rest of the vast, but wonderful place........we went at quite a pace, and were clock watching constantly - this meant it really wasn't as enjoyable as it should have been, and there were still large chunks we missed. there was no time to browse in the gift shops !
Our other annoyance was that there was some wonderful Mexican food available at the place - what meal token did Disney issue ?...burger & chips

.......considering the cost of this excursion, this we felt was very poor - shame on you Disney !
Also the free ice cream you are supposed to be entitled to, we found none of the staff knew anything about it (although we were not bothered, the kids were !!)
Loved the park

, but really it does not make for a good cruise ship excursion due to the limited time IMO.