הזיהויים של patoknight

This is a hatchling Ph. trilineata. They were abundant in this area, as on the previous day, we saw three of them during one hour at a similar habitat, but a couple of kilometers to the south, in Chubut Province.
But, this animal was brought to me some octopus-fishing people who were searching for the mollusks out in the rocky pools exposed at low tide. When they gave me the snake they said that they had captured it while wading in the channel of the estuary that drains the Arroyo Sjenka (picture 4). This location surprised me a lot, as the water there would be a mixture of fresh and salt water, and could have been flowing quite rapidly. But, it is possible that when they found the animal the tide was rising and at equilibrium with the water flowing out of the arroyo, and so was not actually moving very much. I have never heard of this species found in water, even freshwater. The next day, my doubts were removed. Another couple of visitors to the place told me that they had seen a snake in these same waters earlier in the morning. They couldn't say what species they saw, but given that the Ph. trilineata were the only snakes that I saw here over the course of four days, it is probable that they too saw a swimming Ph. trilineata.