The worlds tallest water slide is almost ready for the public — it just needs a little bit more testing before it opens later this year. The Verrückt at Kansas Citys Schlitterbahn Waterpark is 168 feet tall — taller than Niagara Falls — and riders can hit speeds of up to 65 miles per hour on the way down. Naturally, the rides designers want things to be at their absolute safest lest people fly out in sheer horror. So, for the first human trial, an engineer was strapped down to a massive raft with velcro, and his trip was recorded using a Garmin sports camera. The rest is just insane. …