Thanks -- Here's a quick snap without the long exposure:
It's the inlet for a small stream that feeds a small lake. I pretty much had to abstract it, since there was no good composition otherwise. The far bank was too distant and I couldn't get much closer due to the water level.
Here it is from an aerial perspective in Google Maps:
You can actually see the vortex just above the road. The last two images I posted here were shot 180 degrees in the other direction (SSE), from the other side of the levee when the water was much, much lower.
The "hole" of the vortex appeared to be about half a meter in diameter (maybe a little more) but I'm not sure about the depth of the water. I guess maybe 3 meters or so? Actually it might be more than that since it's directly in the channel next to the entrance gate. But the average depth elsewhere is probably 3m or so. Deep enough to drown, most likely...