Or whatever these are called...? Sort of like a tidal pool, but in this case caused by waves surging on to the beach due to strong winds for a few days. See previous two photos for more about what was going one with the water there.
This was taken at the Elberta beach near the south breakwater on Lake Michigan. Taken on "Windy Wednesday," 10-27-2010. There were very strong and steady winds that day, with gusts over 60 mph!
Here's a short video I took while there. Not great but you can get a feel for what is was like, such as being hard to stand still with the steady 30-40 mph winds, with even bigger gusts.