Riverboarding, also known as hydrospeeding, can itself get pretty extreme. It is a sport where you lie on a floating board and paddle/steer with your feet. It can really give an adrenalin rush on fast moving rivers and rapids.
Besides the freezing temperatures, aren’t glaciers supposed to be super dangerous in other ways? The mountains of ice move in unpredictable ways and contain dangerous crevasses. Such glacial rivers often disappear deep beneath the ice in glacial waterfalls. Fall down one of those and you’ll likely be discovered by a different species, a few millennia from now.
In any case, beautiful shot and definitely something worth a try.