Don't let go of the sledge.
Sledging is like going down a river on a luge with flippers. We thought it would be a fun challenge, but...well, it was fun anyway. We were a group of 9 with 3 guides. They called people by their country of origin because they couldn't remember everyone's names, except for Yumi's because they have a friend named Yumi. This is a common occurrence in New Zealand. For once, Yumi is not being called "Yummy" or "Yo Me" or "Yoyo" or some other variation.
The Dutch guys in our group struggled with the instructions. The first guy accidentally knocked one of the guide's flippers in the river. Another jumped into the river the opposite way he was told. Another ignored the first rule of sledging and let go of his sledge. Yet another missed an "eddy", resting spot, and floated down the river sending a guide to follow. The best was Yumi taking out a guide after "surfing" in a wave. It wasn't until we finished that she found out that she knocked the guide in the head with her sledge.
Compared to South America, we pay a lot more for extreme activities, but it's probably because the health and safety standards are much higher here.