There are moments in a trip where a guide gets tense and quiet as they come around a bend in the river. You see the signal to pull over being passed down from boat to boat and, one by one, each guide directs their raft into an eddy on the side of the river. They hop off, go tie up the boat, and come back to announce:
"We're going to scout a rapid."
You may be confused, since you've done a few big rapids at this point in the trip but haven't pulled over yet. You may be invited along, or maybe asked to stay behind and wait for a few minutes while they go check it out.
If your guide goes alone, they may come back quiet and stoic. When asked what they saw, they may tell you, “it still looks like a rapid." Maybe they'll explain the course they plan on taking. There aren't many jokes told as the boat drifts towards the horizon of the river, loudly churning below the drop.
If you're invited to come along and scout the rapid with your guides, you'll walk a trail along the banks of the river. It's probably rocky, winding, and narrow. You'll come to a point where the rapid emerges in it's entirety. There may be huge rocks sticking out of the river, places where the water pours over boulders like a waterfall, and massive waves crashing back upstream. There may be a large expanse of glassy clear water, and obvious safe path through the churning waves. Your guide may tell you what they plan to do, they things they plan to avoid, how hard you may need to paddle or hold on as you drop into the chaos.
The moment then comes again, where you are back on the boats and in the current. You guide will stand to check their place in the river again, looking vigilant and focused. Then, it happens...you feel the boat pulled into the rapid as you careen down into the racing waters ahead. Waves churn about you as your guide maneuvers through the chunder.
Then, as suddenly as it started, it seems to have ended. You look back around and think, that was it? Your guide is grinning ear to ear with their success, and may announce, “Yeah, it's over.”