Growing up at the foot of Mount Washington and skipping school to hike the strenuous Appalachian trails, Jack McConnell has an understandable wariness when it comes to the water. If anything, that early spring splash into the mountain run-off at Emerald Pool in Pinkham Notch prepared him for his annual August plunge into the frigid water between Minot and Middle Island. One quick dive off the side of his tugboat each summer, just to say he’s done it. Paddle around with the seals for a hoot and a holler, then jump back aboard.