We did cave tubing in Belize in March of '06. The water level should be low at that time of year. There are lots af spots where the water is so shallow that the guides will yell "butts up" so you will know that you need to lift up your butt to avoid hitting the bottom. Still, there were a couple of deep areas but wear a life jacket and you will be fine. I forgot the name of the company we used (we did not book thru the ship) but they required us to wear life jackets.