
This is a tough one. It looks like we are seeing the side of the snake? From that, I would guess it is a juvenile watersnake, probably a Diamondbacked Watersnake (Nerodia rhombifer)
Also, TX is a big state. It would help if you had narrowed it down to at least a part of TX. If you are in the eastern 2/3 of the state, I stick with young Diamondbacked Watersnake. Completely harmless.
Here's an adult from Val Verde County for comparison -

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Chris Harrison
San Antonio, Texas

