My first thought is that is a warm spring. 1) Open, unfrozen water, 2) a frog swimming by, and the redness is just a thicker muck or mud, as someone else pointed out, possibly algae (although, I thought algae only bloomed in stagnant, still water. It’s just a heavy muck that doesn’t silt around like lighter material; and 3) the fact that its activity is constant, like a hot spring you would see in yellowstone. The motion reminds me very much of that activity.
Add to that, the guy holding out his hand as if feeling the warmth of the spring, tells me it’s no creature.
In addition....in the glimpses you see of the dog...he looks like he could be a black Lab...and there is no way you'd keep a Lab out of that water, unless it is *hot*.
And there are no monkeys