I did a leisurely paddle around the lake on Friday -- took about an hour. Yes, that is High Mountain in the distance.
You can BYOB (bring your own boat) or rent one on-site from the Ramsey Outdoor Store.
The preserve was once the Haledon Reservoir. I came across this cool 1906 clipping (below) from the NY Sun -- celebrating work starting on New Jersey's first municipal waterworks. (I wonder if nearby Ewing Avenue was named for the mayor mentioned in the article.)
You can learn more about the preserve and download a trail map here.