The South Jetty of the Columbia River is the longest jetty on the Oregon Coast.
I generally do seawatches along the kilometer or so that goes out into the ocean.
I only rarely walk out to the elbow and have only once gone out further.  It's a
long walk.

If I were to try the bush trick, I would probably get a cut (Christmas-tree-like)
Douglas-fir and mount it somewhere 2-3 km out, rather than all the way out on
the end.  As for camping... I'm getting too old for that, I'd probably take my
chances and just get out there really early in the morning...