Ensure you are at the pier 10-15 minutes before the advised 815 pm time frame. We missed our boat after arriving at the pier at 8:03 pm. The entire boat was packed and the security checkpoints/staff stated that there was "no 815pm time slot," even when I showed them the confirmation for my time slot. They both looked confounded as the boat took off in front of us.
I am very disappointed we did not get to experience this on our short vacation. Be wary of who you book this trip through, ours was through "Chicago Seadog Lakefront Speedboat Tour." I am currently hoping I can still get a refund for this unsatisfied trip.