We didn't sign up on the cruise I was on. We were just told when and where to show up (in our case Evolution at 8:15). The CMs in charge came in, gave out bibs, told us what to expect, then we walked off as a group first to the map for them to show us the route, then we started.
Others have reported signing up in advance and I believe signing (I assume) a waiver, but we did not (the lack of a waiver in particular surprised me as literally EVERY race I've participated in includes that - so I HOPE that was just an oversight with our CMs).
There's one "official" water station - at the entrance to/exit from the bike loop - so you've got at least 4 shots at it if necessary. I carry a bottle with me and was fine - but they also offered to refill it when I re-entered the bike loop.
My one caution - and it's one that I think every runner has to remember all the time - is to try and not start out too fast. On our run, I encountered a girl who had taken off top-speed (and apparently had a pretty sizeable breakfast)...and there was shall we say carbo-unloading along the course.