Giant Climbing Structure Above Water

Date: 7/27/2017

I somehow got to the top of a huge structure made out of wood with inflatable rubber-type cushioning that sat on top of the log structure and hung off in formations one could hold onto and climb or swing down. it was maybe 20 stories high and overlooked a river that runs through the park in my town, except rather than being on solid ground, the giant structure was built in the middle of a lake the river extended to, where dry land ought to be. I saw that my little sister was down on the ground on some kind of floating raft in the water, and she needed my help for some reason. I think I thought she was in danger. I tried to climb/swing down from the log tower by holding onto the inflatable cushions, at one point swinging down to grab hold of a bar below me, at risk of falling. I either missed the bar, or caught it and then fell a moment later - but somehow I ended up falling down towards the water below, a cushiony-raft-thing below me. I went underwater and somehow got beneath the raft, and woke up as I was in the middle of drowning. I had this dream while taking a long nap. I seem to have incredibly vivid, almost lucid dreams often when taking long naps in the afternoon.