Yes we did it with some friends and we thought it was a great adventure and had lots of fun. We booked through the ship even though we are well-traveled and experianced cruisers as it is so far from the ship and you do not want to get stranded there by missing the ship.
I've talked to people who did this they say it was great, however the water can be chilly in the caves and you have to hike on dirt roads, etc to get to the destination. There are so many cool things to see in Belize Im going and wish the cruise stayed a few nights. I choose to snorkle with the rays.Largest barrier reef in the Northern hemisphere lots of sea creatures, also considered Altun Ha a Mayan site. You do a search on port reviews and read peoples experiances in Belize. Have fun!
We did the cave tubing in Feb this year, It's a lot of fun...my wife loved it. The water in the caves is NOT cold and the "hike" on the "dirt road" is no more than a 30 - 40 min walk in the woods (our guide made sure we all stayed togeather and provided a very informative lesson on the area, during the walk.. We went with a tour group called Coral Breeze. I booked it on the internet before we departed. The cost was about $50pp compared with $90 on the ship.(same tour....less people)
We did the Cave tubing in feb.. The walk is a hike through the rainforest. It was beautiful. Wear sturdy shoes that can get wet. Old sneakers, water shoes, closed toed.
We bought hard soled water shoes made by Landsend.com. they were sneakers that could get wet and they were on 30$. We used them for cavetubing and kayaking. The cavetubing itself was amazing. The water is not cold, it's "refreshing" and I'm sure by April it will probably be warmer. We took the excursion through the ship and it was 79$ not 90 as previously commented on. And we had about 24 people in our group which was a nice size and we all quickly became friends. The few extra bucks was well worth the peace of mind as the caves are quite a distance from the ship. This excursion was probably was one my favorites of all time. This was our 7th cruise and we always book through the ship.
We booked on our own, through extreme cave tubing, and while there was no guarantee we would make it back on the ship, it was a close call. But we paid $60, and the same trip (actually, the ship only takes you through one cave, we did two) through Carnival costs $93.
It is great, I loved it. It is a long tour from start to finish, I would book through the cruise line, it maybe a little more in price, however if the tour gets back late they will hold the ship for you, vs booking through a independant company.