Siltcoos is a large shallow (20' max) lake, other than thick weeds and some sunken logs near shore, only issue is whitecaps if the wind comes up strong. Coho season is Oct.1 to Dec.31, that is when I am there a whole lot. Siltcoos has bass, yellow perch, and a few rainbows that people target the rest of the year, coho smolts must be released. Bald Eagles, Osprey, Loons, Herons, all sorts of ducks... Duck hunting in the fall is popular.
Siuslaw doesn't have a large bay, more of a wide estuary from Florence to the ocean (~4 miles), just normal tidal current to be aware of, not much river outflow current except during heavy rainfall times, peak fishing is the fall Chinook run, Aug 1 through October, crabbing good all year down close to the ocean, which is a dangerous area when conditions are rough. from June to October, the crabbing can be good up as high as the 101 bridge and even off the Florence marina.