i agree. the lower columbia is very beautiful. if we started in portland or even longview, we could make a day of it (each way). i think from longview it would be somewhere around 50 miles to the ocean.
there would be a great stop in cathlamet for fuel, drinks, and food. then there is several cool little towns between there and astoria. astoria is a great finish place as it is a beautiful old port town. the columbia river bar starts around there and if the weather permited, we could cross and officially make it to the pacific.
the columbia river bar is the roughest section of water in the u.s. so it can be fun and interesting. big waves, currents fighting against them, and moving sandbars make it the "pacific graveyard".
it's a grand finale
my families place is about halfway there and has a dock/shop in case we needed tools, fuel, etc.