The Smith River is another very clear river to dive in the summer months. In winter, it gets to be pretty wild, cold, and only diveable between storms. It's located on Hwy. 199, and dive sites are generally found within 30 miles or so of Hwy. 1 on the coast. Aside from diving, it's incredibly beautiful.
There are several locations people dive on the Smith. Slant Bridge, where a side-road to Hwy. 199 goes over a deep canyon, has been popular for years among classes, although you'll have to carry your gear down a steep trail to get there. Another popular spot, called 'Wagon Wheel', is found just across from the Del Norte County golf course. The river is similar to the illinois - very rocky and a mix of deep holes and shallow rapids. Depths are up to 60 feet.
We sometimes stopped here after ocean diving for a quick dive to rinse off our gear. (Good excuse). I've seen some huge salmon in here, too. JedidiahSmith state park and campground is a favorite place to spend the weekend, and there's hotels scattered along the river in small towns, and Brookings and Crescent City are not too far away (you'll need to get air there).