The last couple times I tried to get on top of the tube, I couldn't, (it was pretty ridiculous looking, and I sure hope nobody was vlogging/filming that, ha,) so I ended up just going in from underneath, and walking/floating.
Sometimes I used to do that just to be close to the kids' tubes, in case they had issues.
I haven't been in a lazy river in a while, and really want to try that rapids one at Volcano Bay, that looks super fun!