When I worked at Generic Water Park, kicking people out of my lines was one of the best parts of the job. I had to watch the slides first, but I'd always try and watch my line out of my peripheral vision.
One slide was always to worst for cutters and they were always so painfully obvious. I always took great glee in sending both the line cutters and their companions to the back of the line to try again. If they fought me or were generally dicks, then I would happily inform them they were banned from the slide either for a time period or for the rest of the day, depending on the situation.
I always got lots of sputtering objections and threats that they would complain to management and get a refund. These threats just made me laugh. We were encouraged to ban troublemakers from our slides because they would probably try and do something stupid like break a slide rule, break their necks, and sue the park.
The really funny thing was we regularly switched stations to keep us fresh, and once I left that station the next person wouldn't know who you were to enforce the ban.
No one knew this and they'd spend the rest of the day sulking on their towel. Hee hee.