Neil Cox, and Leanne Dyke, both members of Bristol Canoe Club, crossed Iceland with a Packraft (a type of inflatable kayak) in May 2017.
Here is Neil’s write-up, including video, and a river description.
https://www.neilcoxmisadventures.com/packrafting/2017iceland-report
Neil comments: “We believe this is the first recorded source-to-sea descent of the Þjórsá, with Leanne also being the first recorded woman to complete a packraft traverse of Iceland.”