As glaciers melt they form little rivulets which join into bigger streams and some time end up falling into a hole and flows under the glacier.
Hydrospeeding is simple, just walk up the glacier carrying your tiny… well it can hardly be called a boat.
Maybe personal floatation device… without falling to your death in a crevasse.
Then find large enough rivulet to launch in barely above freezing water which will merge with others until it becomes large
enough to send you hurtling at breakneck speeds. Oh, and hope you didn’t pick one that falls into the center of the Earth…
although the warmth might be welcome at that point.
I don’t want to sound negative or judgmental, but… can’t you fools find something warmer to do?
link