In the Hudson River 8 bridges is a 120 mile swimming odyssey. On the Willamette 8 bridges gets you to about the halfway point of the swim. So if swimming under bridges is your thing Portland is the place.
Total distance covered is just under 11 miles (maybe 10.8) current assist is nowhere to be found. The finish is the St. Johns Bridge, which is suitably dramatic. Really the finish is the beach about 20 feet north of the bridge but it is the bridge you have to look at, or not, for the last 3 miles.
I actually got a call out at the pre-race meeting as having traveled furthest for the swim. (Just shy of 3000 miles) Really I didn't fly out to Portland just for the swim. But since we were planning a trip to Portland this summer anyway we might as well come for the weekend of July 12th.
Here is a list of the Bridges and their mileage on the swim
Ross Island (mile 2.5)
Tilikum (mile 2.7)
Marquam (mile 3)
Hawthorne (mile 3.4)
Morrison (mile 3.7)
Burlington Northern (9.5)
St. Johns (finish at 10.8)
Now that I've listed them out I see the halfway point is actually at the Fremont Bridge, which is number 10 and that most of the good spots for spectating are on the first half of the swim.