Logs.

A few years ago, I was dong business with a couple that lived aboard a Canoe
Cove near the mouth of the Fraser River.

Just downstream from them, there was a guy who had some sort of permit to
harvest any loose logs that came floating down the Fraser. Tough life. Just
watch the river all day, and when you see a log floating by run out with a
skiff and drag it to the raft up. When a sufficient number of logs are rafted
together, sell the whole works to a lumber mill and start over. :-)