I observed this Diamond-backed Water Snake in a small pond just off the White Rock Creek Bike Trail in the Lake Highlands area of Dallas, Texas.
The snake emerged from under the water just a few yards/meters from the trail. He proceeded to swim to the heavily vegetated shoreline adjacent to the bike trail. The snake was slowed only momentarily by a log floating in the water.
There was a Yellow-crowned Night Heron waiting in the weeds very close to where the snake was headed, and I was hoping to see some predator/prey action. But, alas, their paths did not cross and the water snake made it safely into the cover on the shore.
Diamond-backed Water Snakes are nonvenomous.