Snakes are strange critters. They know when you are coming because they can detect you through vibrations in the ground, your heat signature and likely any noise you make and they can even smell you. Once they have you located they will seek out a safe place and keep a close watch on you. As soon as you get too close, they are gone. They don't want to be anywhere near you if they can possibly get away so don't corner a snake that can strike if you can avoid it said my grandfather. In the summer they become nocturnal according to my Peterson Field Guide. You may be able to tell I don't know a thing about this particular kind of snake. I had to look it up because I didn't know what it looked like. Had never heard of it even though we used to live in it's range.
Are your nights cool? If they are and you know its den, you might try the heating pad trick. Prop open the mouth of a bag that is laying on a heating pad set on low or medium heat. The snake will crawl in for the warmth. Pull the prop out so the bag falls closed Tie off the top of the bag.
I doubt this will work with your current weather. Once your snake is in the water all bets are off but if you can catch him out, sweeping it into a garbage can with a broom is easy enough if you don't fool around. Cover the can with the lid until you can transport him. Do a search on catching snakes. There are other ideas. Sandy