We sample Winni water at two sites on a weekly basis as part of the UNH Lakes Lay Monitoring Program:
http://winnipesaukeegateway.org/moni.../introduction/
One is a 95' deep site between Governor's and Timber. One test is to lower a black and white secchi disk and looking through a view tube record the depth at which the disk disappears from view.
http://www.geoscientific.com/sampling/index.html#SECCI
Previous results this year were not as deep as last year, 8.5 meters vs 9.5 last year. Today the water was very clear and the secchi depth was 10.2 meters (33.5 feet).
BTW, there was a very sharp thermocline at 8.5 meters.