There are three major rivers in Scotland where you can raft down extreme white waters. River Tay is available year-round but two others are seasonal. The Orchy River offers suitable conditions only a few times in winter, so often the best choice is the seasonal river Tummel. Its route goes down the Highlands through several lochs including Loch Rannoch and Loch Tummel and such formidable obstacles as the "Zig-Zag" or the notorious "Sharks Tooth" and above all – the Falls of Tummel drop.
Though you do not need to have previous experience, white rafting in Rummel is definitely not for the faint-hearted. Rafting sessions are available only on Saturdays from June to September, when a certain amount of water is released from the Clunie Dam by the Scottish Hydro Electric.