Its not that bad. They have a well marked channel because theres a lot of barge traffic through there. I never actually ventured into the rock island sloughs they were way to dangerous looking. Probably lots of bass in there but theres huge reefs then its 40 feet deep very unpredictable. I have been on worse area out in the gorge around celilo. That can get real scary if your not watching. Ive never hit any rocks up there. The rock island channel is cool its like 15 feet then goes all the way to 100 or so. I have a detailed map of the area too.