I remember having a well known fly fishing author on the boat with a couple buddies. We were at Swiftsure on one of those incredible krill bloom days when not only is the fishing great but it's almost sensory overload with the humpback whales, birds, and coho all over the surface. The writer had to catch one with a krill fly. He finally hooked one but his friends were hooking coho hand over fist during the twenty to thirty minutes it took him to hook a coho while matching the hatch. After he landed that fish, he promptly switched to a Flashtail Clouser.
If the bait is larger in profile, another great fly is a Flashtail Half and Half Clouser.