West Hill Pond (Lake) is perhaps the best fresh water dive in the whole state of Connecticut with amazing visibility, fish life and great rock formations. There is also a training platform near the island. During the Summer you can dive from the dock in the park or from the state boat ramp during the off season.
Keep in mind that this is a spring fed lake and if you want warmer water you must dive it in the Summer otherwise in the late Fall and Winter the water can be cold. Great for drysuit.
Here is one of my videos