There are two subspecies of watersnakes found in the range of this work.
BLOTCHED WATER SNAKE
Nerodia erythrogaster transversa
The blotched watersnake is found over most of Texas except the far western portion, the far eastern portion and the southwestern portion.
Adult length is usually 2.5'-3', but the record is around 58". They are one of the less aggressive of the Nerodia. Ths specimen pictured is from San Felipe springs in Del Rio.
HOWEVER, they are still a Nerodia, so expect a defensive attitude.