IMO, you should reconsider a SOT. I fished all year in my Pescador 12 (basically a Tarpon 120). Ive NEVER had a water moccasin even come remotely near me while fishing. But I have came upon snakes myself by not paying attention to my surroundings.
Remember, leave them alone and they will leave you alone. Youll also have a paddle, or a stake out stick you can use to ward them off.
Cold water kayak fishing is more about how you prepare rather than what type of kayak. Layers, noncotton, breathable waters, base layer. In the event that you do "turtle" in cold water, you would have a better chance of re-entry on a SOT than a SINK. Not to mention the stability factor of a SOT over a SINK.
You should really try before you buy. I purchase a Old Town Vapor 10 SINK starting out. Cheap, dry, and it got me on the water. 3 months later, I bought a SOT Pescador 12. The freedom of the SOT was priceless.