Okay, times up. What you are looking at is an 82 foot deep hole filled with water, that regional scuba diving enthusiasts use as a training facility for going underwater with air tanks. Local residents also use it for a good old fashioned swimming hole. The light blue square is the training area at the bottom of the hole. The top of the opening is 80 foot in diameter, with the red balloons offering ropes to help new divers navigate downward (and upward).
The swirl of light blue smudges between the balloons are air bubbles coming up from divers below. The white sparkles at the bottom right are, well, sunlight reflecting off the water's surface.
The city of Santa Rosa has adopted the Blue Hole and built a number of other recreational facilities in its vicinity, including a scuba diving resource and training center. HERE IS A LINK to their website telling about the remarkable geological feature and the associated attractions.
