The pictures don't show because they are on your Facebook page, and it seems linking from Facebook seldom works!
One member posted his method in the first message in that thread. But if you read the other messages, you will see that Facebook is a hard nut to crack. Nothing like a lychee!
Our term for your activity is whitewater rafting when there are rapids and rocks, but on slower rivers where there is little whitewater, people do tie rafts together and casually drift down the river, often consuming many adult beverages.