Hey Map, We just got off last week Liberty of the Seas and we signed the waivers for both rock climbing and flowrider on line. Go to your reservation on line and you will see a spot to sign the waivers. My thirteen year old snowboards so he did not need lessons for flow rider. All his buddies a lot of who do not snowboard did not take lessons and were pros by the end of cruise. The staff helps them out with tips, etc. Lessons are pricy $75 I think for 1/2 hour/ Practice helps to make perfect. The boys loved that flow rider. Rock climbing so so. Sort of once you have done it, that is really it. My husband 50 did it too and he does not snowboard. Again, takes practice to stand up but eventually one gets it.