And I'll concur with both Matt and Joe. There are lots of better pet snakes out there that are captive bred, including salt marsh snakes if you decide you like them. However, that looks to me more like a midland water.
If you do keep it, don't keep it with a lot of water. They are quite prone to skin infections if they are damp. I know this sounds weird since they're water snakes, but it is true. A water bowl similar to what you'd use for a corn or king is fine. Feeding a nutritionally sound diet can be a challenge; look at some of the various threads on feeding garters/ribbons/waters for some further insights on this. On the cedar issue, a few hours shouldn't hurt anything.