The black and green peacock spider is an ideal early season fly. It has the black and green combination that makes flies like the Viva and Montana so popular. The hackle creates a disturbance as the fly is pulled though the water. Fish it either shallow or deep, it will produce.
There are many variants of the fly, but the most effective are the black and peacock spider with either a yellow floss tag or a marabou tail.
If snails are on the water, try one of these on a dead drift or slowly twitched through the water.