There is no cable to follow at Lake Minnewaska. But I've compared swimming in that lake to swimming in bottled water - it's a treat.
I don't know how you count strokes for 400m - razor sharp focus. That's one lap around the buoys - right? I have difficulty counting strokes in 50 meters :-). I pull the lanes at LAVC Aquatics Center, simulated open water - 25y lengths are just not nearly as fun as stretching your wings in any direction across the pool, and imagine I'm swimming in Lake Minnewaska.