Apparently, you weren't kidding.
1) The suction created as the iceberg rolls can drag them underneath the iceberg. Just like when a ship sinks, you don't want to be in the water right next to it.
If you think they could just scramble over the iceberg as if they were log rolling, you'd be wrong. It's unlikely that they'd be fast enough for that.
2) PFD's will make them positively buoyant - obviously. This buoyancy can actually pin them under the iceberg if it rolls on top of them, impeding their escape from under it.
3) If they fell from the iceberg as it rolled, it could slam down on them, knocking the air from their lungs, if it didn't outright kill them.
4) The iceberg was quite close to shore, so it could possibly mash them right into the bottom.
5) If they ended up underneath the iceberg, they could be so disorientated, they might not be able to find their way out from under it, before drowning.
I grew up around that coastline and I know what the dangers are. As kids, my friends and I spent many a spring day on drift ice pans out in the cove where I grew up - but not bergs. We would chase each other as we jumped from pan to pan and sometimes we could end up 50 - 100 feet from shore. We would dare each other to jump smaller and smaller pans - some so small, that they wouldn't be able to take your weight if you stopped. So, you'd have to keep moving if you didn't want to get wet - or worse. And, that water was
cold, as I'm sure you can imagine. If the wind shifted and the ice started to drift away from shore, we could be stranded. If you slipped, you could end up in the drink. Then, it was crawl back up on the ice and high tail it for shore and home before you froze to death.
Then, you'd have to make up a reason for being soaking wet for your mom's benefit. Moms would typically be dead set against this activity. Dads were a bit more ambivalent. It's what
they did as kids. And, it was seen as good training for the seal hunt
, although I never took part in that.
It was all a rite of passage for us kids.
But, we'd never go iceberg climbing. Those guys even acknowledged that a rolling iceberg was dangerous. But, they still did it anyway. Don't get me wrong - if they want to do it and if they aren't putting anyone else in danger, I say go ahead. I just do not believe it to be very smart.