I have used Major Tom before and will be using him again on my Valor cruise in March. As stated above people are linked together in groups of 12 and each group has its own guide. I don't know what other companys have for back up transportation, but Major Tom has at least two back up buses and also a tender boat on call. I'm trying to talk my wife into doing the Cave Tubing/Zip Line Combo. It will probably take the next six months to convince her to go for it.