The cave tubing may seem tame, but not if you're the first group allowed to do it in over a week due to flooding. When we did it, it was still high, fast moving water and they deliberated before finally allowing us to do it on our last day. We had no idea what a wicked ride we were in for and 3 people from our group barely made it out alive.
Two almost went over the "strainer" and had to be rescued by other guests and by grabbing onto an overhanging tree to pull themselves up and out of the current. The guides refused to put themselves at risk and had briefed everyone before that part exactly which way to go, not toward the strainer, but those 2 went with the current, instead of to the left onto a bank. At least those two men had the upper body strength to lift themselves out. It could have been very different otherwise. The guides warned everyone that going over the strainer would mean a sure death and they would not be able to go after them and they needed to follow instructions. At least one cave was impassable because there was not enough head space to breathe and we had to hike around.
Before we went through the last cave, we were told that it was extremely fast and very challenging, and they gave everyone the option to hike around if they wanted. A couple of people hiked. The rest of us formed a daisy chain with our tubes, the student guide in the front, leading. All was going well and very fast, and then the guide in the back started yellling, "Get away from the wall!" repeatedly. Everyone tried, but we were heading straight for it. He yelled, "Kick away from the wall!" repeatedly. Everyone broke apart and kicked away. The girl beside me had her hand on my tube and pushed it as she kicked off the wall. My feet hadn't even touched the wall yet and my tube flipped over and I fell straight down, pushed by the wall current to probably 15 feet deep - WITH my life jacket on. I kicked as hard as I could, holding my breath (with no warning) and I could not go up at all. I could see the current and particles rushing down the cave wall and I remained at that depth. I considered removing my boots, which we were required to wear and wondered why my life jacket didn't work. I was sure I was going to die. I finally remembered the last words, "Kick away from the wall!" and I kicked as hard as I could, and I went immediately flying away and up to the surface, gasping for breath. I continued to fly to the cavern exit, minus my headlamp, where the guide had caught my tube and was waiting desperately for me. They kept asking if I was alright and the instructor I was with said they were checking to see if I was in shock. All of us were shaken but ok after each of our incidents.
In my opinion, the cave river tubing is not always tame. We all had an awesome time, though, and it was certainly an adventure. And yes, I would do it again. Hopefully, not after severe flooding and high fast moving water again.
One day is really very short to do the mainland adventures, but maybe a two-tank local morning dive is possible. The best diving, though, is by the atolls, but that would take more time than you could safely allow to get back in time to meet your ship.