Sometimes folks just need a reminder that a go-around is an option.
You can be as nice or as mean about it as you like, but emulating the wise old CFIs you've had in the right seat usually works fine.
"You think this is going to work out, or you want to go try this again?" Assuming enough altitude of course.
I watched a long out of currency CFI save my butt and his one day sitting in the right seat of a chartered 182 on floats. The Otter had gone down for maintenance so the charter company sent "Old Pilot" in one airplane and "Newbie" in the second to load out all of us and out gear.
Old Pilot loaded up his passengers and stuff and blasted off. Newbie took longer and was fussing over things but smiling the whole time. He decided for W&B he wanted me in back, and old military IP up front. We were really tail heavy, and the backs of the floats were not exactly anywhere near level with the fronts. (I was playing passenger that day and freshly minted pilot. I didn't pay much attention. IP WAS paying attention.)
Newbie got us all stuffed in and taxied out to the middle of the lake and downwind a ways to have plenty of takeoff room. He guns it and now even I start to notice the nose wants to be up not down and he's pushing forward a LOT to get the floats on the step. Not trimmed right at all and he's muscling it instead of trimming. IP noticed too but does nothing yet. Just observing.
Airspeed finally comes up after a very long takeoff run on the lake to where newbie wants it, and he pulls. And I mean really that he doesn't just let off some of his forward pressure, he lets the yoke start backward at an alarming rate and the nose digs skyward.
Sometime between the start of the takeoff run and now, the IP has his arm locked to his leg and his hand palm flat to the yoke, ready to stop it's rearward travel at a spot where the airplane won't stall, and we all go for a swim or end up in the trees.
Newbie may or may not have ever noticed the yoke stopped moving back too soon. Old out of currency and not flying anymore IPs hand stopped it.
He pushes forward again in surprise that the nose came up that fast, and manages to finally reach for the trim and gets the nose to stay down enough to settle into a shallow climb out, instead of a classic departure stall.
Clears the trees and we head for the main lake where they operate from. We talk about various things including the kid's brand new portable GPS on the dash. Nobody I knew even owned one yet.
He beamed and pointed out that it was showing our location and waypoints of all the lakes and cabins they flew to, as user waypoints they had added. He says, "I was a part timer for summer season only last year and they wouldn't let me use it. They make us all learn all the terrain and lakes by sight and pilotage before we're allowed to turn them on. This year I'm allowed to use it but I know these lakes like the back of my hand!"
Not a word said by IP/CFI guy about the yoke thing until later -- long after we were out of the airplane at the lodge waiting for the van to our commercial flight out of Dodge...
"Thanks for catching the yoke earlier."
"Yup. Saw that one coming. Kid will get used to an aft CG and lots of weight on floats by the end of the season."
"If he survives."
"I think he knows what I did."
"I couldn't tell from the back seat. Anyway, first beer at the airport is on me, or at the four hour layover in X."
"I'll take it!"
Subtle, helped him out without him losing face, and we all didn't get to see how fast a 182 sinks when it flips in a lake, that day. Yay. Or whether waterlogged Iridium phones work if we survived it. Or if we remembered our CPR skills.
I'm sure CFIs have plenty of stories of wresting controls away from terrified students but they also learn when the pilot over there in the other seat just needs a little "backstop". I learned a bunch that day, too. No reason to panic the kid, just stay a little further ahead of the airplane than he was and stop the chain of events.