Once spring comes around, you can check out Inflatable Zone for a cheap water trampoline for sale. Inexpensive as far as water trampolines go at least. They aren't really cheap at $700, but I've seen them for as much as $4,500 elsewhere, though bigger. The worst part about getting a water trampoline is lugging it around as they aren't light. Beyond the trampoline, there are other climbing obstacles, too.
Bounce houses and inflatable toys aren't just for kids any more. The adrenaline rush obstacle course is an adult's version of an inflatable toy. A company party I recently attended had one similar that everyone really enjoyed. There were teams involved where whole teams were timed through the obstacle course. Winning teams got trophies as well as top individual times, too. These are a blast to play with, provided the weather cooperates.
If you happen to have an Adrenaline Rush Obstacle Course inflatable at your next company outing / party, be sure to watch the people who have drank a little too much. You do bounce around a bit in there and sometimes climbing up those ramps can be a bit much for people who aren't so coordinated.
If you've ever watched the TV show Wipeout, many of the items you can get from Inflatable Zone feel like they belong on the show. The Adrenaline Rush Obstacle Course is a tamer version of the first round of the show. The water trampoline is a tamer version of the big red balls. I can even imagine lining several of them up one after the other, though I'm not quite sure how safe that would be so cant really recommend doing that. The Zorb soccer is like the elimination round two, where you try to knock out an opponent, quite literally. If you look at other items there, that would fill out the show quite nicely, like one of their large inflatable slides which could start off round three even.
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