Duncan Rock looks to be about 9/10 of a mile north of Tatoosh Island. Tatoosh is the island just NW of the tip of mainland Washington State. Distance wise if your launching from Neah Bay to get to it, its about the same distance as oh say the South end of Lake Washington Coulon Boat ramp to about the 520 floating bridge by Bill Gates house in comparison. Probably a good 15 minute hop on a nice day.

I wouldn't launch from Seiku, that could be quiet the trip to Duncan rock, thats a bit further.

You can find a handy map for just about all the popular fishing rocks and points off the olympic penn and a longitude/latitude distance conversion to miles on the following sites:

Maps: http://www.maptech.com ( shows nautical, nav, and topographical maps...can zoom in and out also )

Longitude/latitude conversion to miles distance calculator: http://www.nau.edu/~cvm/latlongdist.html

Goodluck to ya! Have a blast!

PS- last year the coho were sooo thick out there we didn't even travel a mile from Neah Bay after we launched to find hordes of them.