Li Du had no other choice but to swear on Sophie and his child.
After hearing him swear, the Inuit nodded in satisfaction. He said, "Alright, now I'll tell you what's the most dangerous part of this expedition is: it's the water pressure at a hundred meters. If you're not good at diving — and I mean good — then you'll have to be careful."
Li Du understood him instantly. He asked, "We're diving to the bottom of the lake then? To where the spiral rises from?"
The Inuit confirmed with a nod. "Yes, we are."
Water pressure at a hundred meters deep was terrible, but solving this issue was easy for modern technology. They had a submarine at the camping ground which could enable people to dive down to thousands of meters deep — a hundred meters was nothing.
