I've been seeing a lot of these guys this year while bowfishing.
The caption I found says it's a Midland Water Snake, similar to the Northern Water Snake.
They've been cruising parallel to the shore just a few feet out from the bank. One day I saw over a dozen, and the biggest was almost 4 feet long and as big around as a broom handle.
Wasn't sure if it was legal to shoot, and had no idea what I would do with it once I got it in the boat. Also didn't know about the whole 'is it poisonous' thing.
Other IL snakes are listed here...
http://www.chicagoherp.org/herps/snake/Nsipedon.htm
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